Semiconductor SRAM with alternatively arranged P-well and N-well regions
A semiconductor memory device comprises a cell array having a plurality of SRAM cells arranged in a bit line direction and a word line direction orthogonal to said bit line direction in a matrix; and a peripheral circuit arranged adjacent to the cell array in the bit line direction. The cell array includes first P-well regions and first N-well regions shaped in stripes extending in the bit line direction and arranged alternately in the word line direction. The SRAM cell is formed point-symmetrically in the first P-well region and the first N-well regions located on both sides thereof. The peripheral circuit includes second P-well regions and second N-well regions extending in the bit line direction and arranged alternately in the word line direction.
1. A semiconductor memory device, comprising:
a cell array having a plurality of SRAM cells arranged in a bit line direction and a word line direction orthogonal to said bit line direction in a matrix; and
a peripheral circuit arranged adjacent to said cell array in said bit line direction,
wherein said cell array includes first P-well regions and first N-well regions shaped in stripes extending in said bit line direction and arranged alternately in said word line direction, wherein said SRAM cell is formed point-symmetrically in said first P-well region and said first N-well regions located on both sides thereof,
said peripheral circuit includes second P-well regions and second N-well regions extending in said bit line direction and arranged alternately in said word line direction, and includes a read circuit arranged adjacent to one side of said cell arrays in said bit line direction and operative to read data from said SRAM cell, and
said read circuit is arranged such that the length of a basic circuit pattern thereof in said word line direction is equal to an integer multiple of the length of a circuit pattern of said SRAM cell in said word line direction.
2. The semiconductor memory device according to claim 1 , wherein said first and second P-well regions and said first and second N-well regions are respective continued regions.
3. The semiconductor memory device according to claim 1 , wherein said first and second P-well regions and said first and second N-well regions are respective continued regions with the same width.
4. The semiconductor memory device according to claim 1 , wherein said cell array and said peripheral circuit include transistors formed therein with respective gates extending in said word line direction.
5. The semiconductor memory device according to claim 1 , wherein said first and second P-well regions and said first and second N-well regions include diffused layers formed therein, which are shaped in stripes in parallel with the extension direction of said well regions.
6. The semiconductor memory device according to claim 1 , wherein said peripheral circuit includes a write circuit arranged adjacent to the other side of said cell arrays in said bit line direction and operative to write data to said SRAM cell.
7. A semiconductor memory device, comprising:
a cell array having a plurality of SRAM cells arranged in a bit line direction and a word line direction orthogonal to said bit line direction in a matrix; and
a peripheral circuit arranged adjacent to said cell array in said bit line direction,
wherein said peripheral circuit includes a read circuit having second P-well regions and second N-well regions arranged alternately in said word line direction, a plane orthogonal to said word line is formed as a boundary plane between said regions, and operative to read data output from said SRAM cell in single-ended, and
said read circuit is arranged such that the length of a basic circuit pattern thereof in said word line direction is equal to an integer multiple of the length of a circuit pattern of said SRAM cell in said word line direction.
8. The semiconductor memory device according to claim 7 , wherein said peripheral circuit includes a write circuit arranged adjacent to one side of said cell arrays in said bit line direction and operative to write data to said SRAM cell,
wherein said read circuit is arranged adjacent to the other side of said cell arrays in said bit line direction.
9. The semiconductor memory device according to claim 8 , wherein said bit line includes a first and a second local bit lines,
wherein said write circuit includes a first driving circuit operative to selectively connect said first and second local bit lines with the ground line via a transfer gate, wherein said first driving circuit is activated at the time of writing data to said SRAM cell, wherein said first driving circuit is inactivated at the time other than writing data to said SRAM cell.
10. The semiconductor memory device according to claim 7 , wherein said bit line includes a first and a second local bit lines and a global bit line,
wherein said read circuit includes a gate element having an input terminal connected with said first local bit line, and a second driving circuit operative to connect said global bit line with the ground line in response to the output from said gate element.
11. The semiconductor memory device according to claim 7 , wherein said bit line includes a first and a second local bit lines,
wherein said read circuit is operative to read data via said first local bit line,
wherein said SRAM cell includes a first and a second drive elements operative to drive said first and second local bit lines to the ground potential, said first drive element having a higher driving force than said second drive element.
12. A semiconductor memory device, comprising:
a cell array having a plurality of SRAM cells arranged in a bit line direction and a word line direction orthogonal to said bit line direction in a matrix; and
a peripheral circuit arranged adjacent to said cell array in said bit line direction,
wherein said cell array and said peripheral circuit include transistors formed therein with respective gates extending in the same direction,
said peripheral circuit includes a read circuit arranged adjacent to one side of said cell arrays in said bit line direction and operative to read data from said SRAM cell, and
said read circuit is arranged such that the length in said word line direction is equal to an integer multiple of the layout of said SRAM cell.
13. The semiconductor memory device according to claim 12 , wherein said peripheral circuit includes a write circuit arranged adjacent to the other side of said cell arrays in said bit line direction and operative to write data to said SRAM cell.
14. The semiconductor memory device according to claim 12 , wherein said bit line includes a first and a second local bit lines,
wherein said read circuit is operative to read data via said first local bit line, and
said SRAM cell includes a first and a second drive elements operative to drive said first and second local bit lines to the ground potential, said first drive element having a higher driving force than said second drive element.