Patent ID: 8089093

Claim:
A nitride semiconductor device comprising: a substrate having an electrode disposed on a main surface of said substrate, wherein said substrate is a nitride semiconductor substrate, said main surface of said substrate has a first region and a second region, said first region including a first n-type impurity, a concentration of said first n-type impurity in the first region is a higher concentration than a concentration of a second n-type impurity in the second region; wherein said nitride semiconductor substrate includes said second n-type impurity in the second region that is chemically different than said first n-type impurity; said second n-type impurity is oxygen; a concentration of said second n-type impurity is distributed unevenly in said main surface; and another main surface which is an opposite surface from said main surface includes a device structure comprising a plurality of stacked nitride semiconductor layers, wherein the device structure on said another main surface is formed over both a high concentration region and a low concentration region of said second n-type impurity.