Abstract: A semiconductor device having a reflecting layer consisting of unit semiconductors each consisting of two or more semiconductor films of different compositions. The thickness of the unit semiconductors varies continuously or in steps in the direction of thickness of the reflecting layer, preferably decreases in the direction toward the light incidence surface of the layer. For example, the reflecting layer has a varying-thickness portion whose unit semiconductors have a continuously varying thickness, and may include an iso-thickness portion whose semiconductors have the same thickness. The composition at the interface of the adjacent films preferably changes to mitigate a lattice mismatch which causes crystal defects of the layer.