US Patent 7990760 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.