PROBLEM TO BE SOLVED: To minimize surface bonding through an electrical insulating element which comes in contact directly with the side face of an emitter mesa by a method, wherein a III-V semiconductor material, having the same width as that of a mesa, which comes into contact with the free surface of the base and the side face of the mesa, is used as the base material.
SOLUTION: The mesa of a base is etched by dry etching or composite etching, and ohmic contacts 81 and 82 are formed. Then, after the formation of the ohmic contact of the base having the shape of a metal layer 94 by automatic matching with the emitter mesa, the external base is etched for the purpose of reducing the parasitic capacitance of a base collector. A metal covering material can be formed with a Ti/Pt/Au alloy, for example, or with an Mo/Au alloy. A thick element 61 displays superior long-term stability for developing thick passivation, and after the regulation of emitter mesa using a fire-proof metal 42, the hydrogen in the base can be removed easily.