Patent ID: 7157297

Claim:
A method for fabricating a nitride semiconductor device, the method including: a first step of forming a processed substrate by forming, on a nitride semiconductor substrate of which at least part of a surface is a nitride semiconductor or on a substrate formed by laying a nitride semiconductor thin film on top of such a nitride semiconductor substrate, an engraved region formed as at least one depressed portion and a ridge portion formed as an non-engraved region; and a second step of laying a nitride semiconductor layer portion consisting of a plurality of nitride semiconductor thin films both on the engraved region and on a surface of the ridge portion formed on the processed substrate, wherein, in the first and second steps, let 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 the surface of the ridge portion parallel to the surface of the ridge portion be A, and let a sectional area occupied by the nitride semiconductor thin films laid in the depressed portion be B, then B/A, indicating a degree in which the depressed portion is filled by the nitride semiconductor thin films, is 0.8 or less.