US Patent 9761302 Static random access memory cell and manufacturing method thereof

A SRAM cell includes a first pass-gate device and a second-pass gate device comprising a first conductivity type, a first pull-down device and a second pull-down device comprising the first conductivity type, and a first pull-up device and a second pull-up device comprising a second conductivity type complementary to the first conductivity type. The first pass-gate device and the second pass-gate device respectively include first lightly-doped drains (hereinafter abbreviated as LDDs. The first pull-down device and the second pull-down device respectively include second LDDs. And a dosage of the first LDDs is different from a dosage of the second LDDs.