A semiconductor device, such as an inductor, is formed with an air gap. A first level has an intra-metal dielectric layer including one or more inductor loops, one or more vias, and one or more copper bulkhead structures. An inter-level dielectric layer is formed over the first level. An extraction via is formed through the intra-metal dielectric layer and inter-level dielectric layer. An air gap is formed between inductor loops by removing portions of the intra-metal dielectric layer coupled to the extraction via using a supercritical fluid process, and forming a non-conformal layer to seal the extraction via. The air gap may be filled with an inert gas, like argon or nitrogen.