Epitaxial layers in source/drain contacts and methods of forming the same

A method includes providing a p-type S/D epitaxial feature and an n-type source/drain (S/D) epitaxial feature, forming a semiconductor material layer over the n-type S/D epitaxial feature and the p-type S/D epitaxial feature, processing the semiconductor material layer with a germanium-containing gas, where the processing of the semiconductor material layer forms a germanium-containing layer over the semiconductor material layer, etching the germanium-containing layer, where the etching of the germanium-containing layer removes the germanium-containing layer formed over the n-type S/D epitaxial feature and the semiconductor material layer formed over the p-type S/D epitaxial feature, and forming a first S/D contact over the semiconductor material layer remaining over the n-type S/D epitaxial feature and a second S/D contact over the p-type S/D epitaxial feature. The semiconductor material layer may have a composition similar to that of the n-type S/D epitaxial feature.