Provided is a method for manufacturing a MOSFET, including: forming a shallow trench isolation (STI) in a semiconductor substrate to define an active region for the MOSFET; performing etching with the STI as a mask, to expose a surface of the semiconductor substrate, and to protrude a portion of the STI with respect to the surface of the semiconductor substrate, resulting in a protruding portion; forming a first spacer on sidewalls of the protruding portion; forming a gate stack on the semiconductor substrate; forming a second spacer surrounding the gate stack; forming openings in the semiconductor substrate with the STI, the gate stack, the first spacer and the second spacer as a mask; epitaxially growing a semiconductor layer with a bottom surface and sidewalls of each of the openings as a growth seed layer; and performing ion implantation into the semiconductor layer to form source and drain regions.