A method for manufacturing a semiconductor single crystal of a Group III nitride and a method of manufacturing a GaN substrate

The present invention provides a method of Group III nitride semiconductor crystal having excellent crystallinity manufactured for and a method of manufacturing a GaN substrate having excellent crystallinity for, the method comprising melting back control . Specifically, a mask layer on the GaN substrate used as a growth substrate. Thereafter, a plurality of trenches through the masking layer and reach the GaN substrate is formed by photolithography. Obtaining a single crystal seed crystal and the raw material is fed into a crucible and subjected to treatment at high temperature and pressure conditions. In the manipulation of the substrate is exposed to a flux of GaN groove portion undergoes melting back. By dissolving the GaN substrate, the grooves increase in size, to provide a large trench. GaN layer is grown from the mask layer as a starting point of a surface.