To provide a producing method of a semiconductor device for suppressing deterioration in a gate structure and also provide the semiconductor device.

The method of producing semiconductor device comprises steps of forming a tentative gate pattern by laminating a gate insulating film 3 and SiN 4 on a Si substrate 1, forming a source 5 and a drain 5 which are partially embedded in the Si substrate 1 and separated in both sides of the tentative gate pattern, forming SiO2 4 on the source 5, drain 5 and SiN 4, forming SiN 8 at the side surface of a gate opening part formed by flattening SiO2 4 and removing SiN 4, and embedding a gate electrode material 9 in the gate opening part.