Method for forming transistor of semiconductor device

Abstract

A method for forming a transistor of a semiconductor device, includes 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 by filling the trench with oxide; removing an upper portion of the isolation oxide film until an upper lateral portion 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 until the pad nitride film is exposed; performing a wet etching process until the active region is exposed; forming a photoresist pattern over the active region and the barrier nitride film; and performing a dry etching process by using the photoresist pattern as an etching mask, thereby forming a recessed gate trench.