Patent ID: 6927149

Claim:
A method for fabricating a nitride semiconductor device comprising: a lateral growth step in which a nitride semiconductor layer is formed by growing crystals of a group III nitride in a lateral direction on a substrate having trenches each formed of a cavity and peaks formed from group III nitride on the surface thereof with the upper surfaces of the peaks serving as seed crystals, and a multilayered structure formation step for forming a multilayered structure in which a nitride semiconductor multilayered structure having an active layer is formed on the surface of the nitride semiconductor layer, wherein the lattice constant of the substrate is different from that of the group III nitride, the substrate has a mask formed from a dielectric, crystals of the group III nitride are grown in a lateral direction at a temperature not less than 900° C., the mask is formed only on the side surfaces of the peaks, the upper surfaces of the peaks are exposed and the substrate is exposed in the trenches, a height L 1 of the mask is not less than 50 nm and not more than 5000 nm, a width L 2 of the trench is not less than 5000 nm and not more than 50000 nm, and an aspect ratio L 1 /L 2 of the trench is not less than 0.001 and not more than 1.0.