PURPOSE: To purify the manufacturing steps of a C-MOSFET and to improve the controllability by sequentially forming an insulating film and a polycrystalline semiconductor layer on a substrate, and implanting from the ion implantation preventive layer having the prescribed hole formed on the layer to the substrate with reverse conductive type impurity.

CONSTITUTION: A gate insulating film 5 of the prescribed thickness is formed on a one-conductive type semiconductor substrate 1, and a polycrystalline semiconductor layer 7 is formed on the film 5 by a CVD method. Then, an ion implantation preventive layer (resist layer) 3 having a hole 8 is formed on the layer 7. With the layer 3 as a mask reverse conductive type impurity to the substrate 1 is implanted from the hole 8. This impurity is implanted through the layer 7 and the film 5 to the surface directly under the hole 8 of the substrate 1. The layer 3 used as the mask is removed, an insular region 4 having the reverse conductive type is formed, a gate electrode 6 is formed by polycrystalline silicon on the film 5, the manufacturing step of C-MOSFET is simplified to improve the controllability.