A method for fabricating fin-shaped field-effect transistor (FinFET) is disclosed. The method includes the steps of: providing a substrate; forming a fin-shaped structure in the substrate; forming a shallow trench isolation (STI) on the substrate and around the bottom portion of the fin-shaped structure; forming a first gate structure on the STI and the fin-shaped structure; and removing a portion of the STI for exposing the sidewalls of the STI underneath the first gate structure.