PURPOSE: To obtain the semiconductor variable resistant element which facilitates a multiplication process of analog signals, i.e. modulation, demodulation, frequency conversion of signals, by utilizing the fact that the resistance in a base region is varied in inverse proportion to an emitter current.

CONSTITUTION: The carrier concentration in an emitter region 4 is made sufficiently denser than that in the base region 5, and the junction part between a collector and the base is kept to be zero bias or reverse bias. In this way, the minority carriers injected from the emitter region can be made to remain in the base region 5 directly beneath said emitter with almost no loss. The amount of the minority carriers present in the entire area of said base region 5 is proportional to the emitter current over the broad range of the emitter current. Therefore, the electric conductivity in the base region 5 directly beneath the emitter is varied in proportion to the emitter current. That is, the resistance of said base region 5 is reduced in inverse proportion to the emitter current.