Abstract: A field effect transistor comprising a substrate, at least one gate structure, spacers and strained source and drain regions is described. The at least one gate structure is disposed on the substrate and between the recesses and the isolation structures. The spacers are disposed on sidewalls of the at least one gate structure. The strained source and drain regions are disposed in the recesses and on two opposite sides of the at least one gate structure, and top edges of the strained source and drain regions are covered by the spacers and located beneath the spacers.