Patent ID: 7329908

Claim:
A nitride-based compound semiconductor electron device comprising: a substrate; and a semiconductor layer structure including a buffer layer structure, a channel layer and a donor layer, that are consecutively formed in this order on said substrate, wherein: said buffer layer structure includes: at least one first buffer layer comprising as a main component thereof a compound semiconductor expressed by the general formula of Al x In y Ga 1-x-y As u P v N 1-u-v (where 0≦x≦1, 0≦y≦1, x+y≦1, 0≦u <1, 0≦v<1, and u+v<1); and at least one second buffer layer comprising as a main component thereof a compound semiconductor expressed by the general formula of Al a In b Ga 1-a-b As c P d N 1-c-d (where 0≦a≦1, 0≦b≦1, a+b≦1, 0≦c<1, 0≦d<1, and c+d<1), wherein said first buffer layer and said second buffer layer have different bandgap energies, and have two-dimensional electron gas density or densities therein not greater than 5×10 12 cm −2 ; and said first and second buffer layers comprising one of Mg, Be, Zn, and C in an amount of not less than 1×10 16 cm −3 and not greater than 1×10 21 cm −3 ; and said first buffer layer having a thickness of not less than 0.5 nm and not greater than 20 nm, and said second buffer layer has a thickness of not less than 0.5 nm and not greater than 20 nm.