A semiconductor device is disclosed. The semiconductor device includes: a substrate, a gate structure on the substrate, a spacer adjacent to the gate structure, an epitaxial layer in the substrate adjacent to two sides of the spacer, and a dislocation embedded within the epitaxial layer. Preferably, the top surface of the epitaxial layer is lower than the top surface of the substrate, and the top surface of the epitaxial layer has a V-shape.