Method of forming nanosheet transistor structures with reduced parasitic capacitance and improved junction sharpness

摘要

Nanosheet transistor structures with reduced parasitic capacitance and improved junction sharpness generally include a bilayer spacer adjacent a dummy gate disposed on a nanosheet stack. The bilayer spacer includes an inner spacer layer on sidewalls of the gate and a sacrificial layer on the inner spacer layer. The sacrificial layer can be laterally trimmed to bring the in situ doped source/drain regions closer to the channel, which improves junction sharpness. Additionally, the sacrificial spacer layer can be later removed during the process for forming the transistor so as to form an airgap spacer adjacent the gate, which minimizes parasitic capacitance.