A semiconductor device according to the present disclosure includes a source feature and a drain feature, a plurality of semiconductor nanostructures extending between the source feature and the drain feature, a gate structure wrapping around each of the plurality of semiconductor nanostructures, a bottom dielectric layer over the gate structure and the drain feature, a backside power rail disposed over the bottom dielectric layer, and a backside source contact disposed between the source feature and the backside power rail. The backside source contact extends through the bottom dielectric layer.