Patent ID: 7923332

Claim:
A method for producing a semiconductor device, said method comprising the steps of: forming a hard mask layer on a semiconductor substrate, the substrate including a source region; forming a resist layer over said hard mask; patterning said resist layer to form an opening in the resist layer; etching said hard mask to form an opening therein in registry with said opening in said resist layer; removing said resist layer; forming a side wall mask on a sidewall of said mask opening; forming a trench which extends from said opening in said opening in said hard mask to said source region using said side wall mask and said hard mask layer as a mask; removing said side wall mask; coating a sidewall and floor of said trench with an insulating film; forming a gate electrode by filling said trench and said mask opening with a gate electrode material; removing said hard mask to expose a portion of said gate electrode extending above a surface of said substrate; forming a side wall on the side wall of said gate electrode; and forming a drain region below the surface of said semiconductor substrate adjacent to said gate electrode.