摘要 |
The disclosure relates to a semiconductor device. An exemplary structure for a field effect transistor comprises a substrate comprising a major surface and a cavity below the major surface; a gate stack on the major surface of the substrate; a spacer adjoining one side of the gate stack; a shallow trench isolations (STI) region disposed on the side of the gate stack, wherein the STI region is within the substrate; and a source/drain (S/D) structure distributed between the gate stack and STI region, wherein the S/D structure comprises a strained material in the cavity, wherein a lattice constant of the strained material is different from a lattice constant of the substrate; and a S/D extension disposed between the substrate and strained material, wherein the S/D extension comprises a portion extending below the spacer and substantially vertical to the major surface. |