A semiconductor device structure according to the present disclosure includes a source feature and a drain feature, at least one channel structure extending between the source feature and the drain feature, a gate structure wrapped around each of the at least one channel structure, a semiconductor layer over the gate structure, a dielectric layer over the semiconductor layer, a doped semiconductor feature extending through the semiconductor layer and the dielectric layer to be in contact with the source feature, a metal contact plug over the doped semiconductor feature, and a buried power rail disposed over the metal contact plug.