To provide the manufacturing method of a semiconductor device for preventing impurity ions from going through a gate electrode in ion implantation, when forming source/drain regions.

A polysilicon film 9 is formed on a gate insulating film 7, a first resist film 14 is formed on the polysilicon film, and by etching with the resist film as a mask, a first gate electrode 9a is formed on the gate insulating film 7. An N-type impurity is subjected to ion implantation with the first resist film as a mask, thus forming diffusion layers 17 and 18 of the source/drain regions on a silicon substrate 1, forming a second resist film 15 on the polysilicon film. By etching with the second resist film as a mask, a second gate electrode 9b is formed on the gate insulating film 7. Also, by ion implantation of a P-type impurity with the second resist film as a mask, diffusion layers 23 and 24 of the source/drain regions are formed on the silicon substrate.