Abstract: A high-speed semiconductor device which comprises an emitter layer, a base layer, a collector layer, a potential barrier layer disposed between the emitter layer and the base layer, and a superlattice disposed between the base layer and the collector layer. The superlattice provides a multitude of quantum-mechanical transmission coefficients which can be applied to linear analog circuits and high frequency circuit. In addition, the high speed semiconductor device may act as a frequency multiplier, providing an output signal having 2n times as many frequencies as an input signal when n is the number of energy pass bands in said superlattice below a predetermined applied voltage.