Multi-gate device and method of fabrication thereof

A method of semiconductor device fabrication, comprising:

• forming a first fin extending from a substrate, the first fin having a source/drain region and a channel region, wherein the first fin includes a first epitaxial layer having a first composition and a second epitaxial layer on the first epitaxial layer, the second epitaxial layer having a second composition;
• forming a second fin extending from the substrate and having a source/drain region and a channel region, wherein the second fin includes the first epitaxial layer and the second epitaxial layer;
• oxidizing the second epitaxial layer of the second fin, while a hard mask layer protects the first fin;
• removing the second epitaxial layer from the source/drain region of the first fin to form a gap;
• filling the gap with a dielectric material;
• and
• while the dielectric material is filled within the gap, growing a first source/drain epitaxial material on at least two surfaces of the first epitaxial layer to form a first source/drain feature on the first fin;
• and
• growing a second source/drain epitaxial material on the first epitaxial layer of the second fin, to form a second source/drain, and wherein the second source/drain epitaxial material are adjacent the oxidized second epitaxial layer.