Patent ID: 7772611

Claim:
A nitride semiconductor device comprising: a substrate comprising a nitride semiconductor the substrate further comprising an engraved region and a ridge portion, the engraved region comprising a depression portion; and a nitride semiconductor layer formed on the substrate so as to be in direct contact with the ridge portion, a bottom surface of the engraved region, and a side surface of the engraved region, wherein when a sectional area of a region surrounded by a sectional portion of the depressed portion cut along a plane perpendicular to a direction in which the depressed portion extends and lines extending from a top surface of the ridge portion parallel to the top surface of the ridge portion is denoted A, and a sectional area occupied by the nitride semiconductor layer laid in the depressed portion is denoted B, then B/A, indicating a degree in which the depressed portion is filled by the nitride semiconductor layer, is 0.8 or less but greater than 0.