Semiconductor device and method for producing same

A semiconductor device formed in the form of a GaN-based stacked layer including an n-type drift layer, a p-type layer located on the n-type drift layer, and an n-type top layer located on the p-type layer,

• the GaN-based stacked layer having an opening that extends from the n-type top layer and reaches the n-type drift layer through the p-type layer, the semiconductor device comprising:
• a regrown layer located so as to cover a portion of the GaN-based stacked layer that is exposed to the opening, the regrown layer including a channel,
• wherein the regrown layer includes an electron drift layer and an electron supply layer, and the channel is two-dimensional electron gas formed at an interface between the electron drift layer and the electron supply layer, and
• when the electron drift layer is assumed to have a thickness of d, the p-type layer has a thickness in the range of d to 10d, and a graded p-type impurity layer whose concentration decreases from a p-type impurity concentration in the p-type layer is formed so as to extend from a (p-type layer/n-type top layer) interface to the inside of the n-type top layer.