A semiconductor device includes a PMOS region and a NMOS region on a substrate, a first fin-shaped structure on the PMOS region, a first single diffusion break (SDB) structure in the first fin-shaped structure, a first gate structure on the first SDB structure, and a second gate structure on the first fin-shaped structure. Preferably, the first gate structure and the second gate structure are of different materials and the first gate structure disposed directly on top of the first SDB structure is a polysilicon gate while the second gate structure disposed on the first fin-shaped structure is a metal gate in the PMOS region.