A semiconductor memory device having a plurality of memory cells each comprising two CMOS inverters cross-coupled to each other and arranged at intersections between a plurality of word lines extending in a column direction and a plurality of complementary data line pairs extending in a row direction; wherein p-channel type load misfets of the memory cells arranged in the column direction are formed on the main surface of an n-type well region in the direction in which the word lines extend, the source regions of the p-channel type load misfets of the memory cells arranged in the column direction are electrically connected to the n-type well region through conductor layers, and each of the conductor layer is formed independently of the memory cells arranged in the column direction. More specifically, the n-type well regions are fed with a first fixed potential, and the source region of each of the p-channel type load misfets is fed with the first fixed potential through the conductor layers which are formed independently.
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0. 31. A semiconductor memory device comprising:
a first and a second memory cell of a static random access memory arranged in a second direction perpendicular to a first direction; each of said first and said second memory cells including an n channel driver misfet, a p channel load misfet, and an interconnect line such that gate electrodes of said driver misfet and said load misfet overlie a main surface of a semiconductor substrate, such that source and drain regions of said driver misfet and said load misfet are formed in said substrate, and such that said interconnect line is electrically connected between said drain region of said driver misfet and said drain region of said load misfet; and a first conductive layer overlying said main surface and formed of the same level layer as said interconnect lines, of said first and second memory cells, wherein said load misfets of said first and second memory cells are arranged, in said second direction, between said driver misfet of said first memory cell and said driver misfet of said second memory cell, wherein said first conductive layer is electrically connected to said source region of said load misfet of said first memory cell and said source region of said load misfet of said second memory cell, wherein said interconnect line of said first memory cell is arranged, in said second direction, adjacent to said interconnect line of said second memory cell such that said first conductive layer formed on the same level layer as said interconnect line is not positioned, in said second direction, between said interconnect line of said first memory cell and said interconnect line of said second memory cell, wherein said interconnect line is spaced apart from said first conductive layer in said first direction, wherein a wiring line is formed of a different level layer than both said first conductive layer and said interconnect lines, and wherein said wiring line is electrically connected to said source regions of said load misfets through said first conductive layer.
14. A semiconductor memory device comprising:
a wiring line extending in a first direction; a first and a second memory cell of a static random access memory arranged in a second direction perpendicular to said first direction; each of said first and said second memory cells including an n channel driver misfet, a p channel load misfet, and an interconnect line such that gate electrodes of said driver misfet and said load misfet overlie a main surface of a semiconductor substrate, such that source and drain regions of said driver misfet and said load misfet are formed in said substrate, and such that said interconnect line is electrically connected between said drain region of said driver misfet and said drain region of said load misfet; and a first conductive layer overlying said main surface and formed of the same level layer as said interconnect lines, of said first and second memory cells, wherein said load misfets of said first and second memory cells are arranged, in said second direction, between said driver misfet of said first memory cell and said driver misfet of said second memory cell, wherein said first conductive layer is electrically connected to said source region of said load misfet of said first memory cell and said source region of said load misfet of said second memory cell, wherein said interconnect line of said first memory cell is arranged, in said second direction, adjacent to said interconnect line of said second memory cell such that said first conductive layer formed on the same level layer as said interconnect line is not positioned, in said second direction, between said interconnect line of said first memory cell and said interconnect line of said second memory cell, wherein said interconnect line is spaced apart from said first conductive layer in said first direction, wherein said wiring line is formed of a different level layer than both said first conductive layer and said interconnect lines, and wherein said wiring line is electrically connected to said source regions of said load misfets through said first conductive layer.
0. 26. A semiconductor memory device comprising:
a first and a second memory cell of a static random access memory arranged in a second direction perpendicular to a first direction; each of said first and said second memory cells including an n channel driver misfet, a p channel load misfet, and an interconnect line such that gate electrodes of said driver misfet and said load misfet overlie a main surface of a semiconductor substrate, such that source and drain regions of said driver misfet and said load misfet are formed in said substrate, and such that said interconnect line is electrically connected between said drain region of said driver misfet and said drain region of said load misfet; and a first conductive layer overlying said main surface and formed of the same level layer as said interconnect lines, of said first and second memory cells, wherein said load misfets of said first and second memory cells are arranged, in said second direction, between said driver misfet of said first memory cell and said driver misfet of said second memory cell, wherein, in each of said memory cell, said driver misfet is arranged, in said second direction, adjacent to said load misfet, wherein said first conductive layer is electrically connected to said source region of said load misfet of said first memory cell and said source region of said load misfet of said second memory cell, wherein, in each of said memory cells, said interconnect line substantially extends in said second direction, wherein said interconnect line of said first memory cell is arranged, in said second direction, adjacent to said interconnect line of said second memory cell such that said first conductive layer formed of the same level layer as said interconnect line is not positioned, in said second direction, between said interconnect line of said first memory cell and said second interconnect line of said second memory cell, wherein said interconnect lines are spaced apart from said first conductive layer in said first direction, wherein a wiring line is formed of a different level layer than both said first conductive layer and said interconnect lines, and wherein said wiring line is electrically connected to said source regions of said load misfets through said first conductive layer.
9. A semiconductor memory device comprising:
a wiring line extending in a first direction; a first and a second memory cell of a static random access memory arranged in a second direction perpendicular to said first direction; each of said first and said second memory cells including an n channel driver misfet, a p channel load misfet, and an interconnect line such that gate electrodes of said driver misfet and said load misfet overlie a main surface of a semiconductor substrate, such that source and drain regions of said driver misfet and said load misfet are formed in said substrate, and such that said interconnect line is electrically connected between said drain region of said driver misfet and said drain region of said load misfet; and a first conductive layer overlying said main surface and formed of the same level layer as said interconnect lines, of said first and second memory cells, wherein said load misfets of said first and second memory cells are arranged, in said second direction, between said driver misfet of said first memory cell and said driver misfet of said second memory cell, wherein, in each of said memory cell, said driver misfet is arranged, in said second direction, adjacent to said load misfet, wherein said first conductive layer is electrically connected to said source regions of said load misfet of said first memory cell and said source region of said load misfet of said second memory cell, wherein, in each of said memory cells, said interconnect line substantially extends in said second direction, wherein said interconnect line of said first memory cell is arranged, in said second direction, adjacent to said interconnect line of said second memory cell such that said first conductive layer formed of the same level layer as said interconnect line is not positioned, in said second direction, between said interconnect line of said first memory cell and said second interconnect line of said second memory cell, wherein said interconnect lines are spaced apart from said first conductive layer in said first direction, wherein said wiring line is formed of a different level layer than both said first conductive layer and said interconnect lines, and wherein said wiring line is electrically connected to said source regions of said load misfets through said first conductive layer.
0. 18. A semiconductor memory device, comprising:
pairs of first and second memory cells each having transistor regions arranged in a first direction, wherein said first memory cell is arranged adjacent to said second memory cell in a second direction perpendicular to said first direction, each of said first and said second memory cells comprising a pair of n channel misfets, a pair of p channel misfets, and a first and a second interconnect line such that gate electrodes of said n channel misfets and said p channel misfets overlie a main surface of a semiconductor substrate, such that source and drain regions of said n channel misfets and said p channel misfets are formed in said substrate, such that first interconnect line is electrically connected between said drain region of one of said pair of said n channel misfets and said drain region of one of said pair of said p channel misfets, and such that said second interconnect line is electrically connected between said drain region of the other of said pair of said n channel misfets and said drain region of the other of said pair of said p channel misfets, a first conductive layer overlying said main surface and formed of the same level layer as said first and said second interconnect lines, wherein, in said pair of first and said second memory cells, said p channel misfets of said first and said second memory cells are arranged, in said second direction, between said n channel misfets of said first memory cell and said n channel misfets of said second memory cell, wherein, in said pair of said first and second memory cells, said first conductive layer is electrically connected to said source regions of said p channel misfets of said first memory cell and to said source regions of said p channel misfets of said second memory cell, wherein, in said pair of said first and second memory cells, said first interconnect line of said first memory cell is arranged, in said second direction, adjacent to said first interconnect line of said second memory cell such that no conductive layer, including said first conductive layer, formed of the same level layer as said first and said second interconnect lines is positioned, in said second direction, between said first interconnect line of said first memory cell and said first interconnect line of said second memory cell, wherein, in said pair of said first and said second memory cells, said second interconnect line of said first memory cell is arranged, in said second direction, adjacent to said second interconnect line of said second memory cell such that the first conductive layer formed of the same level layer as said first and said second interconnect line is not positioned, in said second direction, between said first interconnect line of said first memory cell and said first interconnect line of said second memory cell, wherein said first and said second interconnect lines are spaced apart from said first conductive layer in said first direction; and a wiring line formed of a different level layer than said first conductive layer and than said first and second interconnect lines, wherein said wiring line is electrically connected to said source regions of said p channel misfets through said first conductive layer.
1. A semiconductor memory device, comprising:
pairs of first and second memory cells each having transistor regions arranged in a first direction, wherein said first memory cell is arranged adjacent to said second memory cell in a second direction perpendicular to said first direction, each of said first and said second memory cells comprising a pair of n channel misfets, a pair of p channel misfets, and a first and a second interconnect line such that gate electrodes of said n channel misfets and said p channel misfets overlie a main surface of a semiconductor substrate, such that source and drain regions of said n channel misfets and said p channel misfets are formed in said substrate, such that first interconnect line is electrically connected between said drain region of one of said pair of said n channel misfets and said drain region of one of said pair of said p channel misfets, and such that said second interconnect line is electrically connected between said drain region of the other of said pair of said n channel misfets and said drain region of the other of said pair of said p channel misfets, a first conductive layer overlying said main surface and formed of the same level layer as said first and said second interconnect lines, wherein, in said pair of first and said second memory cells, said p channel misfets of said first and said second memory cells are arranged, in said second direction, between said n channel misfets of said first memory cell and said n channel misfets of said second memory cell, wherein, in said pair of said first and second memory cells, said first conductive layer is electrically connected to said source regions of said p channel misfets of said first memory cell and to said source regions of said p channel misfets of said second memory cell, wherein, in said pair of said first and said second memory cells, said first interconnect line of said first memory cell is arranged, in said second direction, adjacent to said first interconnect line of said second memory cell such that no conductive layer, including said first conductive layer, formed of the same level layer as said first and said second interconnect lines is positioned, in said second direction, between said first interconnect line of said first memory cell and said first interconnect line of said second memory cell, wherein, in said pair of said first and said second memory cells, said second interconnect line of said first memory cell is arranged, in said second direction, adjacent to said second interconnect line of said second memory cell such that the first conductive layer formed of the same level layer as said first and said second interconnect line is not positioned, in said second direction, between said first interconnect line of said first memory cell and said first interconnect line of said second memory cell, wherein said first and said second interconnect lines are spaced apart from said first conductive layer in said first direction; and a wiring line extending in said first direction and formed of a different level layer than said first conductive layer and than said first and second interconnect lines, wherein said wiring line is electrically connected to said source regions of said p channel misfets of said first and second memory cells through said first conductive layer.
2. A semiconductor memory device according to
3. A semiconductor memory device according to
4. A semiconductor memory device according to
5. A semiconductor memory device according to
6. A semiconductor memory device according to
a second conductive layer overlying said main surface and formed of the same level layer as said first conductive layer; and data lines extending in said second direction and overlying said first and second interconnect lines, each of said memory cells further comprising a first and a second transfer misfet, each of said transfer misfets having a source and a drain region formed in said substrate, wherein one of said source and drain regions of said transfer misfets is electrically connected to said data line through said second conductive layer.
7. A semiconductor memory device according to
8. A semiconductor memory device according to
10. A semiconductor memory device according to
a second conductive layer overlying said main surface and formed of the same level layer as said first conductive layer; and a data line extending in said second direction and overlying said interconnect lines of the first and second memory cells, each of said memory cells further including a transfer misfet having a source and a drain region formed in said substrate, wherein one of said source and drain regions of said transfer misfet is electrically connected to said data line through said second conductive layer.
11. A semiconductor memory device according to
12. A semiconductor memory device according to
13. A semiconductor memory device according to
15. A semiconductor memory device according to
a second conductive layer overlying said main surface and formed of the same level layer as said first conductive layer; and a data line extending in said second direction and overlying said interconnect lines of the first and second memory cells, each of said memory cells further including a transfer misfet having a source and a drain region formed in said substrate, wherein one of said source and drain regions of said transfer misfet is electrically connected to said data line through said second conductive layer.
16. A semiconductor memory device according to
17. A semiconductor memory device according to
0. 19. A semiconductor memory device according to
0. 20. A semiconductor memory device according to
0. 21. A semiconductor memory device according to
0. 22. A semiconductor memory device according to
0. 23. A semiconductor memory device according to
a second conductive layer overlying said main surface and formed of the same level layer as said first conductive layer; and data lines extending in said second direction and overlying said first and second interconnect lines, each of said memory cells further comprising a first and a second transfer misfet, each of said transfer misfets having a source and a drain region formed in said substrate, wherein one of said source and drain regions of said transfer misfets is electrically connected to said data line through said second conductive layer.
0. 24. A semiconductor memory device according to
0. 25. A semiconductor memory device according to
0. 27. A semiconductor memory device according to
a second conductive layer overlying said main surface and formed of the same level layer as said first conductive layer; and a data line extending in said second direction and overlying said interconnect line of the first and second memory cells, each of said memory cells further including a transfer misfet having a source and a drain region formed in said substrate, wherein one of said source and drain regions of said transfer misfet is electrically connected to said data line through said second conductive layer.
0. 28. A semiconductor memory device according to
0. 29. A semiconductor memory device according to
0. 30. A semiconductor memory device according to
0. 32. A semiconductor memory device according to
a second conductive layer overlying said main surface and formed of the same level layer as said first conductive layer; and a data line extending in said second direction and overlying said interconnect lines of the first and second memory cells, each of said memory cells further including a transfer misfet having a source and a drain region formed in said substrate, wherein one of said source and drain regions of said transfer misfet is electrically connected to said data line through said second conductive layer.
0. 33. A semiconductor memory device according to
0. 34. A semiconductor memory device according to
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This is a continuation of application Ser. No. 08/314,775, filed Sep. 29, 1994, U.S. Pat. No. 5,594,270.
The present invention relates to a semiconductor integrated circuit device and, more particularly, to a technology which is effective if applied to a semiconductor integrated circuit device composed of memory cells having a full CMIS (Complementary Metal Insulator Semiconductor) structure.
The memory cells of an SRAM (i.e., Static Random Access Memory) each storing information of 1 [bit] are arranged at intersections between word lines and complementary data lines (complementary data line pairs). A plurality of these SRAM memory cells are arranged in a matrix in the extending directions of the word lines and the complementary data lines to constitute a memory cell array.
Each memory cell of an SRAM is composed of a flip-flop circuit (or an operational amplifier) and two transfer MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The flip-flop circuit is constituted as an information storage unit comprising two drive MOSFETs and two load elements. The two transfer MOSFETs and the two drive MOSFETs are of n-channel conduction type.
The memory cell of the SRAM is exemplified by the full CMOS structure in which the load elements are made up of p-channel conduction type load MOSFETs. The memory cell of this full CMOS structure has its p-channel type load MOSFET, n-channel type drive MOSFET and n-channel type transfer MOSFET all formed in a semiconductor substrate. The memory cell of this full CMOS structure is featured by: (1) a low power consumption; (2) a high speed operation; (3) necessity for neither high resistance polysilicon nor polysilicon PMOS to be laminated over the MOSFETs, but for only the CMOS thereby to simplify the manufacturing process; (4) a stable operation even at a low voltage by the drive of the load MOSFETs; and (5) a high resistance to alpha rays. Thus, the memory cell of the full CMOS structure can be widely used in a super-high speed memory such as a large-sized computer, thanks to the aforementioned feature (2), and in a storage unit of a CMOS logic LSI or microprocessor LSI, thanks to the aforementioned feature (3).
In the memory cell having the full CMOS structure, the source region of the n-channel type drive MOSFET is connected to an operation power line fixed at the operation potential (e.g., -2.5 [V]), and the source region of the p-channel type load MISFET is connected to a reference power line fixed at a reference potential (e.g., 0 [V]). Moreover, the drain regions of the n-channel type drive MOSFET and the p-channel type load MOSFET are connected to each other through intra-cell wirings. The power supply line, the reference potential line and the internal wirings are formed of the first level metal wiring layer. Still moreover, either the source region or the drain region of the n-channel type transfer MOSFET is connected through the intra-cell wirings with complementary data lines formed of the second level metal wiring layer.
Incidentally, the memory cell of the SRAM having the aforementioned complete CMOS structure is disclosed in Japanese Patent Application No. 294576/1992, for example.
We have found out the following problems of the aforementioned SRAM.
In this SRAM, all the power supply line, the reference potential line and the intra-cell wirings are formed of the first level metal wiring layer. Since the size of the memory cell is determined by the first level metal wiring layer, it is difficult to reduce the memory cell size even if the semiconductor elements such as the drive MOSFETs, the transfer MOSFETs and the load MOSFETs are miniaturized.
In the memory cell region, more specifically, the power supply lines and the reference potential lines individually extend in the same direction as that of the word lines, and the intra-cell wirings for connecting the drain regions of the p-channel type load MOSFET and the n-channel type drive MOSFET with each other extend between the power supply line and the reference potential line in the direction perpendicular to the word lines (i.e., in the direction in which the complementary data lines extend).
Between the power supply lines of the memory cells adjacent to each other in the extending direction of the complementary data lines, moreover, there arranged the intra-cell wirings for connecting the n-channel type transfer MOSFET and the complementary data lines.
These power supply line, reference potential line and intra-cell wirings are formed at distances no less than the minimum process size of the wirings. Thus, there arises the aforementioned problem that the size of the memory cell is enlarged.
An object of the present invention is to provide a technology capable of reducing the size of memory cells in a semiconductor integrated circuit device and having the full CMIS structure. Another object of the present invention is to provide a technology capable of achieving the aforementioned object and to enhance the degree of integration of the semiconductor integrated circuit device having the memory cells of the full CMIS structure.
The foregoing and other objects and novel features of the present invention will become apparent from the following description to be made with reference to the accompanying drawings.
A representative of the invention to be disclosed herein will be briefly described in the following.
According to the present invention, there is provided a semiconductor memory device comprising) word lines extending in a column direction, complementary data lines extending in a row direction, and memory cells having first and second inverters which are arranged at the intersections between the word lines and complementary data lines, in each of which the drain regions of a p-channel type load MISFETs and a n-channel type drive MISFET are electrically connected to each other, the gate electrodes thereof are electrically connected to each other, the source region of the p-channel type load MISFET is coupled to a first fixed potential line, and the source region of the n-channel type MISFET is coupled to a second fixed potential line, and the inputs and outputs of which are cross-coupled to each other; wherein the p-channel type load MISEFETs of a plurality of memory cells arranged in the column direction are formed in n-channel well regions in the direction in which the word lines extend, and the source regions of the p-channel type load MISFETs of the memory cells and the n-type well regions are electrically connected to each other through conductor layers, which are formed independently of the plurality of memory cells arranged in the column direction.
By the above-specified means, the well regions can be used as the power supply line to feed the reference potential (or earth potential) or the operation potential (or power supply potential) to the source region of the load MISFET of each memory cell. As a result, it is possible to eliminate the power supply line formed of the first level metal wiring layer on the memory cell and to reduce the cell size of the memory cell.
Since the cell size of the memory cell can be thus reduced, it is possible to enhance the degree of integration of the semiconductor integrated circuit device which is composed of the memory cells having the full CMIS structure.
The present invention will be described in connection with its construction together with one embodiment in which the present invention is applied to a semiconductor integrated circuit device having a logic circuit and a storage circuit.
Incidentally, throughout all Figures for explaining the embodiments, the components having identical functions are designated by common reference symbols so that their repeated description may be omitted.
The layout of a semiconductor integrated circuit device having a logic circuit and a storage circuit in accordance with the present invention is shown in a chip layout diagram in FIG. 1.
As shown in
In this RAM macro 4, as shown in a layout diagram in
The memory mat 5 has a structure, as shown in a layout diagram in
The memory cell 7A is arranged, as shown in an equivalent circuit diagram in
One of the source and drain regions of each of the two transfer MISFETs Qt1 and Qt2 is connected with each of a pair of input/output terminals of the flip-flop circuit. The other of the source and drain regions of the transfer MISFET Qt1 is connected with the first data line DL1, and the gate electrode is connected with the word line WL. The other of the source and drain regions of the transfer MISFET Qt2 is connected with the second data line DL2, and the gate electrode connected with the word line WL. These two MISFETs Qt1 and Qt2 are individually of n-channel type.
The aforementioned flip-flop circuit is composed of two drive MISFETs Qd1 and Qd2 and two load MISFETs Qp1 and Qp2. The two drive MISFETs Qd1 and Qd2 are individually of n-channel type. The two load MISFETs Qp1 and Qp2 are individually of p- channel type. In short, the memory cell 7A of the SRAM of the this embodiment is constructed of the full CMIS structure.
The drain regions of the drive MISFET Qd1 and the load MISFET Qp1 are electrically connected with each other, and the gate electrodes are electrically connected with each other, thus constituting a CMIS inverter circuit. Likewise, the drain regions of the drive MISFET Qd2 and the load MISFET Qp2 are electrically connected with each other and the gate electrodes are electrically connected with each other, thus constituting a CMIS inverter circuit. The individual drain regions (or storage nodes) of the drive MISFET Qd1 and the load MISFET Qp1 are electrically connected with one of the source and drain regions of the transfer MISFET Qt1 and are electrically connected with the individual gate electrodes of the drive MISFET Qd2 and the load MISFET Qp2. The individual drain regions (or storage nodes) of the drive MISFET Qd2 and the load MISFET Qp2 are electrically connected with one of the source and drain regions of the transfer MISFET Qt2 and are electrically connected with the individual gate electrodes of the drive MISFET Qd1 and the load MISFET Qp1.
The source regions of the two drive MISFETs Qd1 and Qd2 are fixed at a power potential VEM (e.g., -2.5 [V]). On the other hand, the source regions of the two load MISFETs Qp1 and Qp2 are fixed at a reference potential VCC (e.g., 0 [V]).
Here will be described a specific structure of the memory cell array 7 with reference to
Incidentally,
As shown in
The memory cells 7A of the memory cell array 7 are formed, as shown in
The aforementioned load MISFET Qp1 is formed, as shown in
The aforementioned drive MISFET Qd1 is formed, as shown in
The aforementioned MISFETs Qt1 and Qt2 are individually constructed like the drive MISFET Qd1, although not shown.
The aforementioned n-type well region 13 and p-type well region 14 are individually formed on the main surface of a semiconductor substrate 10, as shown in FIG. 9. This semiconductor substrate 10 has a so-called SOI (Silicon On Insulator) structure, for example, by stacking an n--type semiconductor substrate 10C made of single crystal silicon on the main surface of an n--type semiconductor support substrate 10A made of single crystal silicon through an insulating film 10B and by growing a silicon epitaxial layer 10D on the main surface of the n--type semiconductor substrate 10C.
The aforementioned field insulating film 15 is formed on the element isolating region (or inactive region) of the main surface of the semiconductor substrate 10. This field insulating film 15 is formed by a well-known selective thermal oxidation method, for example. The aforementioned gate insulating film 18 and insulating film 10B are individually formed of silicon oxide films, for example. The aforementioned isolating groove 16 is made in the main surface of the semiconductor substrate 10 to reach the insulating film 10B. In this isolating groove 16, there is buried an insulating film 17 which is formed of a silicon oxide film, for example.
Below the aforementioned n-type well region 13, there is formed an n+-type semiconductor region 11 whose impurity concentration is set to be higher than that of the n-type well region 13. This n+-type semiconductor region 11 is formed to extend in the extending direction of the n-type well region 13, as shown in
To the n+-type semiconductor region 20 or the source region of the aforementioned drive MISFET Qd1, as shown in
To the n+-type semiconductor region 20 or the drain region of the aforementioned drive MISFET Qd1, there is electrically connected, through the connection hole 22a, one of intra-cell wirings 23B. Likewise, to the n+-type semiconductor region (20) or the drain region of the aforementioned drive MISFET Qd2, there is electrically connected, through the connection hole 22a, the other of the intra-cell wirings 23B. These intra-cell wirings 23B are formed of the first level metal wiring layer and extend in the row direction.
To the p+-type semiconductor region 21 or the drain region of the aforementioned load MISFET Qp1, there is electrically connected, through the connection hole 22a formed in the interlayer insulating film 22, one of the intra-cell wirings 23B. Likewise, to the p+-type semiconductor region (21) or the drain region of the aforementioned load MISFET Qp2, there is electrically connected, through the connection hole 22a, the other of the intra-cell wirings 23B. In other words, the p+-type semiconductor region 21 or the drain region of the load MISFET Qp1 is electrically connected through one of the intracell wirings 23B to the n+-type semiconductor region 20 or the drain region of the drive MISFET Qd1, and the p+-type semiconductor region (21) or the drain region of the load MISFET Qp2 is electrically connected through the other internal wiring 23B to the n+-type semiconductor region (20) or the drain region of the drive MISFET Qd2.
To the p+-type semiconductor region 21 or the source region of the load MISFET Qp1, as shown in
The aforementioned other intra-cell wiring 23A is electrically connected through the connection hole 22a to an n+-type semiconductor region 20A formed on the main surface of the n-type well region 13. Likewise, the aforementioned one internal wiring 23A is electrically connected through the connection hole 22a to the n+-type semiconductor region (20A). In other words, the n+-type semiconductor region 21 or the source region of the load MISFET Qp2 is electrically connected to the n+-type semiconductor region 11 through the one intra-cell wiring 23A, the n+-type semiconductor region 20A and the n-type well region 13, and the p+-type semiconductor region 21 or the source region of the load MISFET Qp1 is electrically connected to the n+-type semiconductor region 11 through the other intra-cell wiring 23A, the n+-type semiconductor region 20A and the n-type well region 13. The n+-type semiconductor regions 20A are individually formed with a view to enhancing the ohmic contact characteristics with the internal wirings 23A, in the same manufacturing step of the n+-type semiconductor regions 20 or the source region and the drain region of the drive MISFET Qd2.
The aforementioned other intra-cell wiring 23A is electrically connected through the connection hole 22a to the n+-type semiconductor region 21 or the source region of the load MISFET (Qp2) of another memory cell 7A adjacent in the column direction. Likewise, the one intra-cell wiring 23A is electrically connected through the connection hole 22a to the n+-type semiconductor region 21 or the source region of the load MISFET (Qp1) of the aforementioned another memory cell. In short, the intra-cell wirings 23A are made integral with the two memory cells 7A adjacent to each other in the row direction. Thanks to this construction in which the intra-cell wirings 23A are made integral with the two memory cells 7A adjacent to each other in the column direction, the area to be occupied by the intra-cell wirings 23A can be reduced to reduce the cell size of the memory cells 7A.
The gate electrode 19 of the aforementioned load MISFET Qp1 is made integral with the gate electrode 19 of the drive MISFET Qd1. Likewise, the gate electrode 19 of the aforementioned load MISFET Qp2 is made integral with the gate electrode 19 of the drive MISFET Qd2. These gate electrodes 19 are, individually formed in the step of forming the first level polysilicon wiring layer, and a multilayer film or refractory metal films 19B over a polycrystalline silicon film 19A, for example.
The gate electrodes 19 of the aforementioned load MISFET Qp1 and drive MISFET Qd1 are electrically connected to the other intra-cell wiring 23B, and the gate electrodes 19 of the aforementioned load MISFET Qp2 and drive MISFET Qd2 are electrically connected to the one intra-cell wiring 23B. In other words, the gate electrodes 19 of the load MISFET Qp1 and the drive MISFET Qd1 are electrically connected to the individual drain regions (21 and 20) of the load MISFET Qp2 and the drive MISFET Qd2, the individual gate electrodes 19 of which are electrically connected to the individual drain regions (21 and 20) of the load MISFET Qp1 and the drive MISFET Qd1.
The gates electrodes 19 of the aforementioned transfer MISFETs Qt1 and Qt2 are made integral with the word lines WL. In other words, the gate electrodes 19 of the transfer MISFETs Qt1 and Qt2 are electrically connected to the word lines WL. These word lines WL are formed of the first level poly-silicon wiring layer.
The one n+-type semiconductor region (20) of the aforementioned transfer MISFET Qt1 is made integral with the n+-type semiconductor region 20 or the drain region of the drive MISFET Qd1. Likewise, the one n+-type semiconductor region (20) of the aforementioned transfer MISFET Qt2 is made integral with the n+-type semiconductor region 20 or the drain region of the drive MISFET Qd2. In other words, the one n+-type semiconductor region 20 of the transfer MISFET Qt1 is electrically connected to the individual drain regions (20 and 21) of the drive MISFET Qd1 and the load MISFET Qp1, and the one n+-type semiconductor region (20) of the transfer MISFET Qt2 is electrically connected to the individual drain regions (21 and 20) of the MISFETs Qd2 and Qt2.
To the other n+-type semiconductor region (20) of the aforementioned transfer MISFET Qt1, there is electrically connected, through the connection hole 22a, one intra-cell wiring 23C. Likewise, to the other n+- type semiconductor region (20) of the aforementioned transfer MISFET Qt2, there is electrically connected, through the connection hole 22a, the other intra-cell wiring 23C. These intracell wirings 23C are individually formed of the first level metal wiring layer.
The aforementioned one internal wiring 23C is electrically connected, as shown in
The memory cells 7A thus constructed are arranged in plurality in the extending direction of the word lines WL and in plurality in the extending direction of the first data line DL1 and the second data line DL2.
Here will be described a specific structure of the power supply cell 8A with reference to
As shown in
The aforementioned power supply line 25A is electrically connected through the connection hole 24a formed in the interlayer insulating film 24 to a wiring line 23D. This wiring line 23D is formed of the first-level metal wiring layer. The wiring line 23D is electrically connected through the connection hole 22a formed in the interlayer insulating film 22 to an n+-type semiconductor region 20B. This n+-type semiconductor region 20B is formed in the main surface of the n-type well region 13 in the area surrounded by the field insulating film 15. The n+-type semiconductor region 20B is formed in the same step of forming the aforementioned n+-type semiconductor region 20A.
The aforementioned n+-type semiconductor region 20B is electrically connected to an n+-type semiconductor region 11A. This n+-type semiconductor region 11A is formed in the n-type well region 13 in the area surrounded by the field insulating film 15 and is electrically connected to the n+-type semiconductor region 11. The n+-type semiconductor region 11A is formed in the same step of forming a heavily doped semiconductor region for the contact with the collector of a bipolar transistor used in the aforementioned peripheral circuit.
To the aforementioned n+-type semiconductor region 11 and n-type well region 13, the power supply line 25A is electrically connected through the n+-type semiconductor region 11A, the n+-type semiconductor region 20B and the wiring line 23D. In short, the n+-type semiconductor region 11 and the n-type well region 13 are fixed at the reference potential (e.g., 0 [V]).
The n+-type semiconductor region 11 formed below the aforementioned n-type well region 13 is electrically connected, as described above, to the individual source regions (21) of the load MISFETs Qp1 and Qp2 through the n-type well region 13, the n+-type semiconductor region 20A and the intra-cell wiring 23A. In other words, the n+-type semiconductor region 11 and n-type well region 13 are used as the power supply lines, and the source regions (21) of the load MISFETs Qp1 and Qp2 are fixed at the reference potential (e.g., 0 [V]). Thus, the n+-type semiconductor region 11 and the n-type well region 13 are fixed at the reference potential and are used as the power supply lines, so that the source regions (21) of the load MISFETs Qp1 and Qp2 of each memory cell 7A are applied with the reference potential. As a result, the power supply lines formed of the first level metal wiring layer on the memory cell 7A can be eliminated to reduce the size of the memory cell 7A.
The memory size reduction will be more specifically described with reference to FIG. 25.
Since, moreover, the aforementioned n-type wells 13 are used as the power supply lines, there arises no process increase caused by the formation of a special region for the power supply.
Incidentally, the power supply lines 25B are electrically connected to the p-type well region 14 through the wiring formed of the first level metal wiring layer. Moreover, wirings 25C are electrically connected to not only the power supply lines 23 but also the power supply lines which are formed of the third level metal wiring layer. These power supply lines are fixed at the operation potential (e.g., -2.5 [V]) and extend in the same direction as the extending direction of the power supply lines 23. Still, moreover, wirings 25D are electrically connected to not only the word lines WL but also the word line backing wiring (i.e., the word shunting wiring) formed of the third level metal wiring layer. These backing wiring extend in the same direction as that of the word lines WL.
The power supply cells 8A thus constructed are arranged on both sides of each memory cell array 9 composed of sixteen memory cells 7A, as shown in
Here will be briefly described a specific structure of the aforementioned logic circuit unit 2 with reference to
As shown in
Each standard cell 2A is composed of a p- channel MISFET Qp and an n-channel MISFET Qn. Of these, the p-channel MISFET Qp is formed on the main surface of the n-type well region 13 in the area surrounded by the field insulating film 15. In other words, the p-channel MISFET Qp is composed of the n-type well region (channel forming region) 13, the gate insulating film, the gate electrode 19, and the p+-type semiconductor regions 21 of the source and drain regions. Likewise, the n-channel MISFET Qn is formed on the main surface of the p-type well region 14 in the area surrounded by the field insulating film 15. In other words, the n-channel MISFET Qn is composed of the p-type well region (channel forming region) 14, the gate insulating film, the gate electrode 19, and the n+-type semiconductor regions 20 of the source and drain regions.
To the p+-type semiconductor region 21 or the drain region of the aforementioned p-channel MISFET Qp, the n+-type semiconductor region 20 or the drain region of the n-channel MISFET Qn is electrically connected through an internal wiring 23G. To the p+-type semiconductor region 21 or the source region of the p-channel MISFET Qp, a power supply line 23F extending in the column direction is electrically connected. To the n+-type semiconductor region 20 or the source region of the n-channel MISFET Qn, a power supply line 23E extending in the column direction is electrically connected. The internal wiring 23G, the power supply line 23E and the power supply line 23F are individually formed in the first level metal wiring layer.
To the power supply line 23E, a power supply line 25E which is formed in the second level metal wiring layer is electrically connected. To the power supply line 25E, moreover, a power supply line 25F which is formed in the second level metal wiring layer is electrically connected. These power supply lines 25E and 25F individually extend in the column direction. The power supply line 25E is fixed at the operation potential whereas the power supply line 25F is fixed at the reference potential. In other words, the n+-type semiconductor region 20 or the source region of the n-channel MISFET Qn is fixed at the operation potential whereas the p+-type semiconductor region 21 or the source region of the p-channel MISFET Qp is fixed at the reference potential.
Here will be described the operations of the aforementioned memory cells 7A with reference to the accompanying drawings.
At the reading time, the word line WL of the corresponding bit is selected so that a cell current I1 flows from the first data line DL1 to the VEM through a storage node S1 of the Low side, as shown in
At the writing time, on the other hand, the potential of the first data line DL1 pm the High side is lowered by a write circuit 30, as shown in
In the memory cell 7A of the full CMIS structure, the storage node (S2) at the Low level is instantly changed to the High level by the driving force of the load MISFET. In the high-resistance load memory cell 31, on the contrary, the current flowing out from the VCC is so extremely low because of a high load resistance (of about 100 megaohms) that it takes a long time (of 1 s or more) to reach the completely High potential. Since the potential difference between the righthand and lefthand storage nodes is small in this meanwhile, the storage charge of the storage nodes is so small that the strength against the alpha rays is low.
In short, the VEM wiring resistor R2 raises a problem at the reading time, and the VCC wiring resistor R1 raises a problem at the writing time.
Then, the VCC wiring resistor will be studied. Since the n-type well region 13 and the n+-type semiconductor region 11 are used for the VCC wiring, the resistance is higher than that of when the first level metal wiring layer is used. In the full CMIS memory cell 7A, the load element is the p-channel type MISFET, the driving force of which is used to achieve the ultrahigh speed, the stability and the resistance to the alpha rays. As a result, the VCC wiring is equipped with a high resistance, the driving force of the PMOS is substantially weakened to deteriorate the merit of the CMIS memory cell.
However, the ON resistance of the load MISFET is about 10 [KΩ]. Hence, the high-speed operation is not adversely affected if the power supply line resistance is lower than one tenth of that value, i.e., about 1 [KΩ]. Even when the power supply line resistance is several tens [KΩ], the resistance is lower than those of the high-resistance load memory cell (of 100 [MΩ] or more) and the poly-silicon PMOS load (the ON resistance is 1 [MΩ] or more), so that the driving force of the load PMOS can be exploited. Thus, the CMIS memory cell 7A is far more advantageous in terms of high speed operation and stability. For reference,
In the embodiment, the n+-type semiconductor region 11 and the n-type well region 13 have sheet resistance of about 30 [Ω], the n+-type semiconductor region 11 and the n-type well region 13 have widths of 4 microns, and the distance between the power supply cells 8A is about 80 microns. The resistance of the n+-type semiconductor region 11 and the n-type well region 13 from the memory cell 7A the farthest from the power supply cell 8A to the power supply cell 8A (located just at the midpoint from the cells) is about 300 [Ω]. Since the power supply line resistance is about 150 [Ω], as viewed from the memory cell 7A, there is no influence at all considering that the power supply cells 8A are provided on both sides. Even when, moreover, the n+-type semiconductor region 11 is not used in the CMIS process, the sheet resistance of the n-type well region 13 is about 1 [KΩ], so that the power supply line resistance is about 5 [KΩ], and there is no influence.
Here will be examined the VEM wiring resistor R2 in the following (with reference to FIG. 16). At the reading operation, a voltage drop is established in the resistor by the current I1 to float the source potential of the drive MISFET. If the upper limit of this potential rise is set to about 1 [V] and if the current I1 is set to about 0.1 [mA], the VEM wiring resistor R1 has an upper limit of about 10 [KΩ].
It can be understood from the description made above that the n+-type semiconductor region 11 and the n-type well region 13 are remarkably effectively used as the power supply lines for the memory cells 7A.
Incidentally, in the embodiment, the n+- type semiconductor region 11 and the n-type well region 13 are used as the power supply lines, but the p- type well region 12 may be used as the power supply line to eliminate the power supply line 23 which is formed of the first level metal wiring layer.
As shown in
As shown in
As shown in
As shown in
As shown in
Thus, the following operational effects can be achieved by the present embodiment.
The n-type well region 13 is used as the power supply line and the reference potential or the power potential can be applied to the individual source regions of the load MISFETs Qp1 and Qp2 of each memory cell 7A. As a result, the power supply line formed of the first level metal wiring layer on the memory cell 7A can be eliminated to reduce the cell size of the memory cells 7A.
Moreover, the p-type well region 14 is used as the power supply line, the reference potential or the operation potential can be applied to the individual source regions of the drive MISFETs Qd1 and Qd2 of each memory cell 7A. As a result, the power supply line formed of the first level metal wiring layer on the memory cell 7A can be eliminated to further reduce the cell size of the memory cells 7A.
By forming the n+-type semiconductor region 11 below the n-type well region 13, still moreover, the resistance of the power supply line can be lowered.
By forming the p+-type semiconductor region 12 below the p-type well region 14, furthermore, the resistance of the power supply line can be lowered.
In the two memory cells 7A adjacent in the row direction, furthermore, the intra-cell wirings 23A are made integral, so that the cell size of the memory cells 7A can be further reduced.
Furthermore, the cell size of the memory cells 7A can be reduced, thereby enhancing the degree of integration of the semiconductor integrated circuit device having the memory cells 7A of the full CMIS structure.
Although our invention has been specifically de scribed on the basis of the foregoing embodiment, it should not be limited to the embodiment but can naturally modified in various manners without departing from the gist thereof.
Hiramoto, Toshiro, Tamba, Nobuo, Kasai, Motoki
Patent | Priority | Assignee | Title |
8044437, | May 16 2005 | AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LIMITED | Integrated circuit cell architecture configurable for memory or logic elements |
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