Patent ID: 7361518

Claim:
A method for fabricating a semiconductor element comprising: a first step of producing a processed substrate by forming, on a substrate having a nitride semiconductor layer as at least part of a surface thereof, an engraved region including at least one depressed portion and a ridge portion as a non-engraved region; and a second step of laying a nitride-semiconductor layered-structure portion including at least one type of nitride semiconductor thin film both in the engraved region and on a surface of the ridge portion, wherein, in the first step, the engraved region is so formed as to include two or more depressed portions and a narrow flat portion sandwiched therebetween, the narrow flat portion having a width of 100 μm or less in a direction perpendicular to a first direction in which the engraved region extends, and wherein, in the second step, a first dummy-ridge portion is formed on a region of the ridge portion close to the engraved region by making a thickness of the nitride semiconductor layered-structure portion laid on the region of the ridge portion close to the engraved region as measured from the surface of the ridge portion to a surface of the nitride semiconductor layered-structure portion greater than a thickness of the nitride semiconductor layered-structure portion laid on a semiconductor element production region, which is a region of the ridge portion other than the region thereof close to the engraved region, as measured from the surface of the ridge portion to the surface of the nitride semiconductor layered-structure portion, and a second dummy-ridge portion is formed in the narrow flat portion by making a thickness of the nitride semiconductor layered-structure portion laid on the narrow flat portion as measured from the surface of the narrow flat portion to the surface of the nitride semiconductor layered-structure portion greater than the thickness of the nitride semiconductor layered-structure portion laid on the semiconductor element production region as measured from the surface of the ridge portion to the surface of the nitride semiconductor layered-structure portion.