Patent ID: 8513077

Claim:
A method of manufacturing a semiconductor device, comprising: forming a channel layer in a surface of a semiconductor substrate; forming a silicon nitride film directly on the surface of the semiconductor substrate, forming a first silicon dioxide film on the silicon nitride film, and providing an opening for forming a trench in the silicon nitride film and the first silicon dioxide film, both of the silicon nitride film and the first silicon dioxide film covering the channel layer; forming the trench at a position of the opening from the surface of the semiconductor substrate using the silicon nitride film and the first silicon dioxide film as a mask, the trench being formed deeper than the channel layer; removing the first silicon dioxide film while leaving the silicon nitride film; forming a second silicon dioxide film as a gate oxide film on a side surface of the trench using the silicon nitride film as a mask; thereafter depositing a gate electrode material directly on a surface of the silicon nitride film so as to fill the trench and removing the gate electrode material on the silicon nitride film using the silicon nitride film as a mask, to thereby form a gate electrode inside the trench so that an upper end surface of the gate electrode is positioned above a surface of the channel layer to be formed as a source region; and removing the silicon nitride film and then forming the source region at a periphery of the trench, the source region having a conductivity type opposite to a conductivity type of the channel layer.