The present invention provides a semiconductor device, including a substrate, two gate structures disposed on a channel region of the substrate, an epitaxial layer disposed in the substrate between two gate structures, a first dislocation disposed in the epitaxial layer, wherein the profile of the first dislocation has at least two non-parallel slanting lines, and a second dislocation disposed adjacent to a top surface of the epitaxial layer, and the profile of the second dislocation has at least two non-parallel slanting lines.