The present invention discloses a method for manufacturing a semiconductor device, comprising: forming a gate stack structure on a substrate; forming a drain region in the substrate on one side of the gate stack structure; and forming a source region made of GeSn in the substrate on the other side of the gate stack structure; wherein the forming the source region made of GeSn comprises: implanting precursors in the substrate on the other side of the gate stack structure; and performing a laser rapid annealing such that the precursors react to produce GeSn alloy, thereby to constitute a source region; and wherein the step of implanting precursors further comprises: performing a pre-amorphization ion implantation, so as to form an amorphized region in the substrate; and implanting Sn in the amorphized region.