Patent ID: 7760783

Claim:
A semiconductor device comprising: a semiconductor substrate; a semiconductor layer group on the semiconductor substrate, the semiconductor layer group including a first semiconductor layer, a second semiconductor layer and a third semiconductor layer that are formed in order from the substrate side; and a thin film continuously coating an upper surface and side surfaces of the semiconductor layer group, wherein the second semiconductor layer has an etching rate slower than etching rates of the first and third semiconductor layers, wherein a normal vector on a surface coated with the thin film of the semiconductor layer group has an upward component, and wherein the second semiconductor layer comprises InGaAsP or GaAsP, a P mole fraction in Group V elements of the second semiconductor layer is larger than 0.2 but smaller than 0.6, the first and third semiconductor layers each comprise AlGaAs, GaAs or InGaAs, and wherein the second semiconductor layer has a bandgap energy intermediate between bandgap energies of the first and third semiconductor layers.