A method for manufacturing a semiconductor device is provided. The method comprises providing a semiconductor substrate; forming a dummy gate structure and a spacer surrounding the dummy gate structure on the semiconductor substrate; forming source/drain regions on both sides of the gate structure within the semiconductor substrate using the dummy gate structure and the spacer as a mask; forming an interlayer dielectric layer on the upper surface of the semiconductor substrate, the upper surface of the interlayer dielectric layer being flush with the upper surface of the dummy gate structure; removing at least a part of the dummy gate structure so as to form a trench surrounded by the spacer; performing tilt angle ion implantation into the semiconductor substrate using the interlayer dielectric layer and spacer as a mask so as to form an asymmetric Halo implantation region; sequentially forming a gate dielectric layer and a metal gate in the trench.