Patent ID: 7851821

Claim:
A group III nitride semiconductor device, comprising: a group III nitride semiconductor supporting base, the group III nitride semiconductor supporting base being composed of a group III nitride semiconductor, the group III nitride semiconductor supporting base having a primary surface, the primary surface being tilted at a finite angle with reference to a reference plane, the reference plane being orthogonal to a reference axis, and the reference axis extending in a direction of a c-axis of the group III nitride semiconductor; and a gallium nitride based semiconductor region provided on the primary surface of the group III nitride semiconductor supporting base, the gallium nitride based semiconductor region having an oxygen concentration of from 5×10 16 cm −3 to 5×10 18 cm −3 , the primary surface having one of semi-polarity and non-polarity, and the gallium nitride based semiconductor region including a first conductive type gallium nitride based semiconductor layer.