Abstract: A mask for forming a semiconductor layer and a semiconductor device manufactured using the same. The mask for forming a semiconductor layer includes oblique openings. Since a semiconductor layer is formed through one or more openings, it is possible to suppress generation of threading dislocation in a vertical direction from a growth surface of a heterogeneous substrate. The oblique openings are formed by stacking a growth blocking layer on the substrate, followed by dry etching the growth blocking layer, with the substrate disposed in a tilted state.