A semiconductor structure includes a semiconductor fin disposed over a substrate, a metal gate stack disposed over the semiconductor fin, an epitaxial source/drain (S/D) feature disposed over the semiconductor fin and adjacent to the metal gate stack, and a dielectric feature embedded in the semiconductor fin, where a bottom surface of the epitaxial S/D feature is disposed on a top surface of the dielectric feature, and where sidewalls of the epitaxial S/D feature extend to define sidewalls of the dielectric feature.