Method for producing group III nitride-based compound semiconductor device

A method for producing a Group III nitride-based compound semiconductor device in which a hetero-substrate is used as an epitaxial growth substrate and which comprises stacking an epitaxial layer of a Group III nitride-based compound semiconductor on the epitaxial growth substrate, bonding a support substrate to a top surface of the epitaxial layer via a conductive layer, and removing the epitaxial growth substrate by laser lift-off,

• comprising, before bonding the support substrate to the epitaxial layer formed on the epitaxial growth substrate, forming trenches in such a manner as to extend from a top surface of a stacked structure including the epitaxial layer formed on the epitaxial growth substrate to at least an interface between the epitaxial growth substrate and a bottom surface of the epitaxial layer,
• wherein the trenches divide the epitaxial layer formed on the epitaxial growth substrate into extended device areas which encompass respective product device structures, and stress relaxation areas, and
• a plurality of laser irradiations are performed for laser lift-off such that, after each laser irradiation, the expanded device areas and the stress relaxation areas are separated into a laser-irradiated area and a laser-unirradiated area, and a strip-shaped laser-unirradiated stress relaxation area is formed at a boundary between the laser-irradiated area and the laser-unirradiated.