US Patent 10367076 Air gap spacer with controlled air gap height

A FinFET and method for fabricating an air gap spacer in a FinFET is disclosed. The FinFET includes a sidewall spacer between a gate material and an interlayer dielectric material. The sidewall spacer includes a lower portion that extends fully between the gate and the interlayer dielectric material and an upper portion that includes an airgap. The sidewall spacer is fabricated by depositing a sacrificial gate structure in a gate region having an upper sacrificial layer and a lower sacrificial layer, and removing the upper sacrificial layer to expose a sidewall spacer region. Airgap spacer material is deposited in the exposed sidewall spacer region to form an upper portion of the sidewall spacer having the air gap.