A semiconductor device includes a substrate, a logic gate structure, a photosensitive gate structure, a hard mask layer, a first spacer, a first source, a first drain, a second spacer, a second source and a second drain. The logic gate structure and the photosensitive gate structure are disposed on a surface of the substrate. The hard mask layer covers the logic gate structure, the photosensitive gate structure and the surface of the substrate. The first spacer overlies the hard mask layer conformal to a sidewall of the logic gate structure. The first source and drain are respectively disposed in the substrate at two opposite sides of the logic gate structure. The second spacer overlies the hard mask layer conformal to a sidewall of the photosensitive gate structure. The second source and drain are respectively disposed in the substrate at two opposite sides of the photosensitive gate structure.