PURPOSE: To form a floating gate easily without lowering the degree of integration by forming a side-wall oxide film on the side wall of a polysilicon layer to be a floating gate, and providing a spacer oxide film additionally so as to cover the oxide film.

CONSTITUTION: A parallel beltlike laminated part G composed of a polysilicon layer 5a, a silicon nitride film 8, and a silicon oxide film 11 is selectively formed on a thermal oxide film 4 formed on the surface of a semiconductor substrate 1. A side-wall oxide film 5d sacrificial is formed on the side wall of the polysilicon layer 5a of the first conductor layer of the beltlike laminated part G, and a spacer oxide film 7' is formed so as to cover the side-wall oxide film 5d. Consequently, it becomes possible to prevent the length of a gate or channel from shrinking, by suppressing the generation of gate bird's beaks in the next thermal oxidation process by this spacer oxide film 7'. Besides, gate sections G1-G4 are averaged by the spacer oxide film 7'.