Patent ID: 6391700
Filing Date: 2002-05-21
Classification: H01L

Abstract:
A method for forming a semiconductor device having a twin-well region, said method comprising:providing a semiconductor substrate; forming an oxide layer on said semiconductor substrate; patterning a first photo-resist layer on said oxide layer to define a first well region; etching a partial thickness of said oxide layer by said first photo-resist layer as a mask to form an etched region as an alignment mark; performing a first ion-implant process by said first photo-resist layer as a mask and said etched region of said oxide layer as said alignment mark to form an first doped region in said semiconductor substrate; removing said first photo-resist layer; patterning a second photo-resist layer on said etched region of said oxide layer and another desired portion of said oxide layer to define a second well region; performing a second ion-implant process through said first oxide layer into said semiconductor substrate by said second photo-resist layer as a mask to form a second doped region; removing said second photo-resist; performing a drive-in process for activating said first doped region and said second doped region to form said first well region and said second well region; forming a nitride layer along the surface of said oxide layer; patterning a third photo-resist layer on said nitride layer of said first well region and said second well region to define a first actively region and a second actively region on said first well region and said second well region respectively; etching said nitride layer by said third photo-resist layer as a etching mask to form a first nitride region and a second nitride region on said first well region and said second well region respectively; removing said third photo-resist layer; forming a field oxide region between said second nitride layer and said third nitride layer; and removing said first nitride region and said second nitride region to form a semiconductor device having a twin-well region.