Abstract: The present invention provides a semiconductor device and a method for fabricating the same, wherein the method comprises: providing a germanium-based semiconductor substrate having a plurality of active regions and device isolation regions between the plurality of the active regions, wherein a gate dielectric layer and a gate over the gate dielectric layer are provided on the active regions, and the active regions include source and drain extension regions and deep source and drain regions; performing a first ion implantation process with respect to the source and drain extension regions, wherein the ions implanted in the first ion implantation process include silicon or carbon; performing a second ion implantation process with respect to the source and drain extension regions; performing a third ion implantation process with respect to the deep source and drain regions; performing an annealing process with respect to the germanium-based semiconductor substrate which has been subjected to the third ion impla