A method for manufacturing a MOSFET, including: performing ion implantation, via a shallow trench surrounding an active region in a semiconductor substrate, into a first sidewall of the active region and into a second sidewall of the active region opposite to the first sidewall to form a first heavily doped region in the first sidewall and a second heavily doped region in the second sidewall; filling the shallow trench with an insulating material, to form a shallow trench isolation; forming a gate stack and an insulating layer on the substrate, wherein the insulating layer surrounds and caps the gate stack; forming openings in the substrate using the shallow trench isolation, the first and second heavily doped regions, and the insulating layer as a hard mask; and epitaxially growing a semiconductor layer with a bottom surface and sidewalls of each of the openings as a seed layer.