Therefore, when such boron is diffused to obtain a high surface concentration of an order of 1019 -1020 (atoms/cc), crystal defects may be induced in lateral direction from the P type gate diffusion region, i.e. in the channel region CH. When n-type silicon single crystal layer having low impurity concentration of an order of 1014 -1015 (atoms/cc) is epitaxially grown on a surface including the ab