Patent ID: 8488371

Claim:
A static random access memory comprising: a common well of a first conductivity type formed in a semiconductor substrate; a memory cell array formed in said common well and including a plurality of memory cells arranged in a row and column formation such that a group of memory cells aligned in a column direction and connected commonly to a bit line constitute a memory cell column, said plurality of memory cell columns forming a plurality of column groups each including therein a plurality of memory cell columns, said plurality of column groups being repeated in a row direction; a column selection circuit provided to each of said column groups, said column selection circuit being configured to be supplied with a part of address data and selecting consecutively a specific memory cell from said column group corresponding thereto; in each of said plurality of memory cell columns of said memory cell array, there extends a second conductivity type well of a second conductivity type opposite to said first conductivity type for those MOS transistors having a source region and a drain region of said first conductivity type and there extends a first conductivity type well of said first conductivity type for those MOS transistors having a source region and a drain region of said second conductivity type, such that said second conductivity type well and said first conductivity type well extend adjacent with each other in said column direction, in first and second column groups that are adjacent with each other, one of the first conductivity type well of said first memory cell column selected by said first column group and the first conductivity type well of said second memory cell column selected at the same time by said second column group, is isolated from said common well by a deep well of said second conductivity type, said deep well of said second conductivity type being formed deeper than any of said first conductivity type well and said second conductivity type well, said deep well of said second conductivity type has a size not exceeding a size of a column group in said row direction.