US Patent 11488968 Integrated circuit and static random access memory thereof

An IC structure comprises a substrate, a first SRAM cell, and a second SRAM cell. The first SRAM cell is formed over the substrate and comprises a first N-type transistor. The second SRAM cell is formed over the substrate and comprises a second N-type transistor. A gate structure of first N-type transistor of the first SRAM cell has a different work function metal composition than a gate structure of the second N-type transistor of the second SRAM cell.