Since the semiconductor devices including a stacked structure of group-III-V alloy semiconductor layers different in the kind of group-V constituent atom form the so-called band line-up of type II, band discontinuity in the heterostructure has impeded smooth transport of carriers and deteriorated device characteristics. According to the present invention, an energy band structure that makes it possible, in one energy band (e.g., a valence band), to smoothly transport carriers of one of two kinds (e.g., holes) by connecting energy discontinuity in an inclined form or stepwise, and at the same, in the other energy band (e.g., a conduction band), to maintain a barrier effect for carriers of the other kind (e.g., electrons) by retaining energy discontinuity, can be realized for improved transport characteristics of carriers at the heterointerface forming the band line-up of type II.