PURPOSE: To reduce dispersions of Ron and Vth without lowering reverse breakdown strength by making a depth from a substrate region surface shorter than a transverse length of a substrate region which is covered with a gate electrode.

CONSTITUTION: A pattern of a polysilicon electrode 7 is formed by deviating it by δ in reverse direction of a transverse diffusion direction from a P-type pattern by a thermal oxide film 8. As a result, a depth Xjp from a surface of a substrate region 2 is shorter than a transverse length XjpL of a source region surface which is covered with the gate electrode 7. Since a deviation length 6 is provided in this way, a maximum impurity concentration of the substrate region 2 wherein a channel is formed does not change even if a diffusion depth of the substrate region 2 (P) and a source region 3 (n-) shows dispersions a little.