US Patent 9768118 Contact having self-aligned air gap spacers

A semiconductor device includes a semiconductor substrate, and a dielectric layer on an upper surface of the semiconductor substrate. A contact stack is formed in the dielectric layer. The contact stack includes an electrically conductive contact element, and a contact liner on first and second opposing sidewalls of the contact element. A first air gap is interposed between the dielectric layer and the contact liner on the first side wall, and a second air gap interposed between the dielectric layer and the contact liner on the second side wall.