Patent ID: 6900100

Claim:
A process of fabricating a trench semiconductor device comprising: providing a semiconductor material; depositing a hard mask layer over a surface of said semiconductor material; forming an opening in said hard mask layer; etching said semiconductor through said opening in said hard mask layer to form a trench extending from said surface into said semiconductor material, said trench being bounded on one side by a mesa; directionally depositing a thick oxide layer on said semiconductor material, said oxide layer depositing preferentially on horizontal surfaces so as to form a first thick portion in a bottom of said trench and a second thick portion on said hard mask layer, and a thin portion on said sidewall of said trench; removing said thin portion of said thick oxide layer from said sidewall of said trench; growing a gate oxide layer on said sidewall of said trench forming a polysilicon layer in said trench, said polysilicon layer having a surface abutting said hard mask layer; and removing said second thick portion of said thick oxide layer from said hard mask layer, said mesa being protected by said hard mask layer.