GaN film having a reduced threading dislocations density and fabrication method thereof

A semiconductor thin film of e.g. G or N includes an underlying semiconductor layer (2) in which a plurality of facets (1) are arranged, and a selectively grown/buried semiconductor layer (3) formed to cover the underlying semiconductor layer (2), wherein the facets (1) are formed by planes tilted with respect to the disposition plane of the underlying semiconductor layer (2). In this semiconductor thin film, threading-dislocations (d) are formed in the selectively grown/buried semiconductor layer (3) in such a manner that each of the threading-dislocations (d) bendingly extends from one of the facets (1) of the underlying semiconductor layer (2) in the direction substantially along the disposition plane of the underlying semiconductor layer (2), being joined to another of the threading-dislocations (d) bendingly extending from the opposed one of the facets (1), and bendingly extends from the joined portion in the direction crossing the disposition plane of the underlying semiconductor layer (2).