US Patent 11205597 Semiconductor device and method

A method includes forming a first fin extending from a substrate, forming a first gate stack over and along sidewalls of the first fin, forming a first spacer along a sidewall of the first gate stack, the first spacer including a first composition of silicon oxycarbide, forming a second spacer along a sidewall of the first spacer, the second spacer including a second composition of silicon oxycarbide, forming a third spacer along a sidewall of the second spacer, the third spacer including silicon nitride, and forming a first epitaxial source/drain region in the first fin and adjacent the third spacer.