A method includes forming a first fin and a second fin protruding from a semiconductor substrate and defined by a fin height, forming a spacer layer over the first fin and the second fin, etching the spacer layer to form inner spacers and outer spacers along opposite sidewalls of each of the first fin and the second fin, where the inner spacers are formed between the first fin and the second fin and where etching the spacer layer results in the inner spacers to extend above the outer spacers, forming a source/drain (S/D) recess in each of the first fin and the second fin, and forming an epitaxial semiconductor layer in the S/D recesses, where forming the epitaxial semiconductor layer forms an air gap with the inner spacers.