Isolation for multigate devices

Abstract

An exemplary method includes forming a semiconductor fin having a semiconductor layer stack over a semiconductor mesa. The semiconductor layer stack includes a first semiconductor layer, a second semiconductor layer, and the first semiconductor layer is between the semiconductor mesa and the second semiconductor layer. The method further includes forming an isolation feature adjacent the semiconductor mesa and forming a semiconductor cladding layer along a sidewall of the semiconductor layer stack. The semiconductor cladding layer extends below a top surface of the semiconductor mesa and a portion of the isolation feature is between the semiconductor cladding layer and a sidewall of the semiconductor mesa. The method further includes, in a channel region, replacing the first semiconductor layer of the semiconductor fin and the semiconductor cladding layer with a gate stack. The portion of the isolation feature is between the gate stack and the sidewall of the semiconductor mesa.