Patent ID: 8247844

Claim:
A semiconductor device comprising: a channel layer where electrons move; a barrier layer provided on the channel layer and forming two dimensional electron gas in the channel layer; a buffer layer provided under the channel layer; and an isolation layer that is separate from at least a lower portion of the buffer layer and provided between the lower portion of the buffer layer and the channel layer, the isolation layer being configured to suppress a leakage current at least between the channel layer and the buffer layer, wherein the channel layer is a GaN channel layer including GaN, wherein the barrier layer is an AlGaN barrier layer including AlGaN, wherein the buffer layer is a GaN buffer layer including GaN, and wherein the isolation layer includes: a layer that includes AlGaN where the Al content in AlGaN upwardly increases from the GaN buffer layer and where a bandgap upwardly gradually expands from the interface on the side of the buffer layer, and a layer having a superlattice structure that is variant in bandgap and including AlGaN and GaN.