A semiconductor device and a method of forming the same, the semiconductor device includes a substrate, a plurality of fin shaped structures and an insulating layer. The substrate has a fin field-effect transistor (finFET) region, a first region, a second region and a third region. The first region, the second region and the third region have a first surface, a second surface, and a third surface, respectively, where the first surface is relatively higher than the second surface and the second surface is relatively higher than the third surface. The fin shaped structures are disposed on a surface of the fin field-effect transistor region. The insulating layer covers the first surface, the second surface and the third surface.