Patent ID: 7651923

Claim:
A method for forming a transistor of a semiconductor device, the method comprising: forming a trench by etching a semiconductor substrate on which a pad oxide film and a pad nitride film are sequentially formed; forming a isolation oxide film to define an active region by filling the trench with oxide; removing an upper portion of the isolation oxide film until a vertical surface of the semiconductor substrate is exposed; forming a barrier nitride film over the isolation oxide film, the semiconductor substrate, and the pad nitride film; forming a sacrificial oxide film over the barrier nitride film; performing a planarization process on the sacrificial oxide film and the barrier nitride film until the pad nitride film is exposed; performing a wet etching process on a resulting structure until the active region is exposed; forming a photoresist pattern over the active region and a remaining portion of the barrier nitride film; and performing a dry etching process on the active region by using the photoresist pattern as an etching mask, thereby forming a recessed gate trench.