A fin field effect transistor and method of forming the same. The fin field effect transistor comprises a semiconductor substrate having a fin structure and between two trenches with top portions and bottom portions. The fin field effect transistor further comprises shallow trench isolations formed in the bottom portions of the trenches and a gate electrode over the fin structure and the shallow trench isolation, wherein the gate electrode is substantially perpendicular to the fin structure. The fin field effect transistor further comprises a gate dielectric layer along sidewalls of the fin structure and source/drain electrode formed in the fin structure.