A method for producing a semiconductor device includes forming an aluminum layer on a core substrate, anodizing the aluminum layer into an alumina layer having a plurality of nanoholes, forming an n-type GaN layer by growing crystals of a compound semiconductor such as an n-type GaN on the alumina layer and inside the nanoholes, and dissolving the alumina layer with an acid. As a result, gaps are formed and a structure in which the core substrate is joined to the n-type GaN layer through portions, other than the gaps, having a very small area is generated. Then a laser beam is applied to the n-type GaN layer through the core substrate to separate the n-type GaN layer from the core substrate by a laser lift-off technique.