A new functional heterostructure-emitter and heterostructure-base bipolar transistor (HEHBT) with a pseudomorphic quantum-well (QW) base structure is presented. Due to the insertion of an InGaAs quantum well between the emitter-base (E-B) junction, the valence band discontinuity can be enhanced and a high emitter injection efficiency may be achieved. In addition, an interesting Sshaped multiple negative-differential-resistance (MNDR) phenomenon is observed under the inverted operation mode. This may be attributed to an avalanche multiplication and sequential two-stage barrier lowering effect resulting from electrons accumulation at the AlGaAs/GaAs heterointerface and the InGaAs QW, respectively. Consequently, owing to the transistor performance and MNDR characteristics, the HEHBT shows a good promise for amplification and multiplevalued logic circuit applications.