Abstract: A process for fabricating a trench power semiconductor device is disclosed. A first dielectric layer between the pad oxide layer and the mask oxide layer is formed so as to form a gate with a height higher than the surface of the pad oxide layer after the first dielectric layer is removed. In addition, a sidewall structure is formed at laterals of the gate protruded from the surface of the trench structure. Hence the source structure and the first conductive layer formed at the surface of the gate can be isolated through the sidewall structure. When the trench power semiconductor device is processed at high frequency, the net resistance of the gate can be reduced by the first conductive layer, and thus the electrical properties thereof can be elevated.