Interconnect structures and methods for forming an interconnect structure. A sacrificial layer is formed on a substrate and an interconnect opening is formed that extends vertically through the sacrificial layer into the substrate. The interconnect opening is filled with a conductor to form a conductive feature. After filling the interconnect opening with the conductor, a dielectric layer is formed on the sacrificial layer. After the dielectric layer is formed on the sacrificial layer, the sacrificial layer is removed to form an air gap layer arranged vertically between the dielectric layer and the substrate.