A method for fabricating semiconductor device is disclosed. The method includes the steps of: providing a substrate having a fin-shaped structure thereon and shallow trench isolation (STI) around the fin-shaped structure; forming a gate line across the fin-shaped structure and on the STI; performing a first cutting process to remove the part of the gate line directly above the fin-shaped structure and the fin-shaped structure directly under the gate line; and performing a second cutting process to remove part of the gate line on the STI.