A semiconductor device utilizing the resonant-­tunneling effect, such as a light emitting-resonant-tunneling bipolar transistor, comprises stacked first through fifth semiconductor layers (16, 15B₂, 15W, 15B₁, 13). The semiconductor device has an energy level condition of |Ec₃ - Ec₁ |≒|Ev₃ - Ev₅|, where Ec₃ is a resonant energy level of electrons in a conduction band of the third layer (15W) and Ev₃ is a resonant energy level of holes in a valence band thereof, and Ec₁ is an energy level of a conduction band of the first layer (16) and Ev₅ is an energy level of a valence band of the fifth layer (13).