Abstract: A complementary semiconductor device includes P- and N-type semiconductor regions separately formed in a semiconductor substrate and having substantially the same concentration of impurities. N-and P-channel type silicon gate field effect transistors are formed in the P-and N-channel type regions, respectively. Gate electrodes of the P-and N-channel type silicon gate field effect transistors are formed by polycrystalline silicons of the same conductivity type. An impurity of the same conductivity type is doped into both the semiconductor regions to provide channel doped regions.