A semiconductor device with bi-layer dislocation and method of fabricating the semiconductor device is disclosed. The exemplary semiconductor device and method for fabricating the semiconductor device enhance carrier mobility. The method includes providing a substrate having a gate stack. The method further includes performing a first pre-amorphous implantation process on the substrate and forming a first stress film over the substrate. The method also includes performing a first annealing process on the substrate and the first stress film. The method further includes performing a second pre-amorphous implantation process on the annealed substrate, forming a second stress film over the substrate and performing a second annealing process on the substrate and the second stress film.