US Patent 11189705 Methods of reducing parasitic capacitance in multi-gate field-effect transistors

A semiconductor structure includes a stack of semiconductor layers disposed over a substrate, a first metal gate stack disposed over the stack of semiconductor layers, a second metal gate stack interleaved between the stack of semiconductor layers, a source/drain (S/D) feature disposed in the stack of semiconductor layers, and an S/D contact disposed over the S/D feature. In many examples, the S/D feature is separated from a sidewall of the second metal gate stack by a first air gap and the S/D contact is separated from a sidewall of the first metal gate stack by a second air gap.