US Patent 11374104 Methods of reducing capacitance in field-effect transistors

A semiconductor structure includes a fin protruding from a substrate, a first and a second metal gate stacks disposed over the fin, and a dielectric feature defining a sidewall of each of the first and the second metal gate stacks. Furthermore, the dielectric feature includes a two-layer structure, where sidewalls of the first layer are defined by the second layer, and where the first and the second layers have different compositions.