Patent ID: 6991983
Filing Date: 2006-01-31
Classification: H01L

Abstract:
1. A method of manufacturing a high voltage transistor in a flash memory device, comprising: performing a first ion implantation process for controlling a threshold voltage of a high voltage transistor for a semiconductor substrate and for preventing a punch leakage at a bottom of an isolation film; forming a gate oxide film for a high voltage device on the semiconductor substrate; sequentially forming a polysilicon film and a pad nitride film on the resulting structure including the gate oxide film; forming a shallow trench that extends into the semiconductor substrate by sequentially etching a portion of the pad nitride film, the first polysilicon film and the semiconductor substrate; filling the shallow trench with an insulating film to form the isolation film; removing the pad nitride film to expose the polysilicon film; and performing a second ion implantation process to form a source/drain junction of the high voltage transistor.