A semiconductor integrated circuit according to the present invention comprises a semiconductor substrate, a plurality of MOS field effect transistors each formed on a surface region of the semiconductor substrate and having source and drain regions, a gate insulating film formed on a region between the source and drain regions, and a gate electrode formed on the gate insulating film. The gate electrode includes a polycrystalline SiGe-mixed crystal which is expressed by Si.sub.1-x Ge.sub.x (1>x>0).