Nitride semiconductor device

Abstract

A nitride semiconductor device includes a substrate, and a first nitride semiconductor layer, a second nitride semiconductor layer, a third nitride semiconductor layer, and a fourth nitride semiconductor layer sequentially formed on the substrate. A channel is formed in the third nitride semiconductor layer, and includes carriers accumulated near an interface between the third nitride semiconductor layer and the fourth nitride semiconductor layer. The second nitride semiconductor layer has a band gap larger than that of the third nitride semiconductor layer. The first nitride semiconductor layer has a band gap equal to or larger than that of the second nitride semiconductor layer, and has a carbon concentration higher than that of the second nitride semiconductor layer.

Dependencies are inferred from the claim text.