Field effect transistor having an air-gap gate sidewall spacer and method

Abstract

A method is disclosed wherein a gate, having a gate cap and a sacrificial gate sidewall spacer, is formed adjacent to channel region(s) of a transistor and metal plugs, having plug caps, are formed on source/drain regions. The sacrificial gate sidewall spacer is selectively etched, creating a cavity that exposes sidewalls of the gate and gate cap. Optionally, the sidewalls of the gate cap are etched back to widen the upper portion of the cavity. A dielectric spacer layer is deposited to form an air-gap gate sidewall spacer within the cavity. Since different materials are used for the plug caps, gate cap and dielectric spacer layer, a subsequently formed gate contact opening will be self-aligned to the gate. Thus, a gate contact can be formed over an active region (or close thereto) without risk of gate contact-to-metal plug shorting. A structure formed according to the method is also disclosed.