A semiconductor device and a method of fabricating the same, the semiconductor device including a fin structure, a first liner, a first insulating layer and a dummy gate structure. The fin structure is disposed on a substrate, where the fin structure has a trench. The first liner disposed in the trench. The first insulating layer disposed on the first liner. The dummy gate structure is disposed on the first insulating layer and disposed above the trench, where a bottom surface of the dummy gate and a top surface of the fin structure are on a same level.