US Patent 7479657 Semiconductor device including active matrix circuit

There is provided a combination of doping process and use of side walls which allows the source and drain of a thin film transistor of an active matrix circuit to be doped with only one of N-type and P-type impurities and which allows the source and drain of a thin film transistor used in a peripheral circuit of the same conductivity type as that of the thin film transistor of the active matrix circuit to include both of N-type and P-type impurities. Also, a thin film transistor in an active matrix circuit has offset regions by using side walls, and another thin film transistor in a peripheral circuit has a lightly doped region by using side walls.