Abstract: A nitride semiconductor device 1 includes a conductive SiC substrate 2 that has a first surface 2a and a second surface 2b opposite thereto, a semi-insulating SiC layer 3 that is formed in at least a portion of a surface layer portion at the first surface 2a side of the conductive SiC substrate 2, and a nitride epitaxial layer 40 that is formed on the conductive SiC substrate 2 such as to cover the semi-insulating SiC layer 3.

Abstract: A nitride semiconductor device 1 includes an SiC substrate 2 of a hexagonal crystal system that has a first main surface 2a and a second main surface 2b at an opposite side thereof and a nitride epitaxial layer 20 that is formed on the first main surface 2a and the first main surface 2a has an off angle of greater than 1° with respect to a c-plane of the hexagonal crystal.

Abstract: A nitride semiconductor device is a nitride semiconductor device including a substrate that has a first main surface and a second main surface at an opposite side thereto and a nitride epitaxial layer that is formed on the first main surface. The nitride semiconductor device has, in plan view, an active region inside the nitride epitaxial layer in which a two-dimensional electron gas can form and an inactive region inside the nitride epitaxial layer in which the two-dimensional electron gas is not formed and includes trenches that, in at least the inactive region among the active region and the inactive region, are formed in the substrate and are dug in from the second main surface toward the first main surface and embedded metals that are formed inside the trenches.