PURPOSE: To make high sufficiently a current gain by a method wherein after the mesa structure of a heterojunction bipolar transistor is formed, a surface treatment is performed using sulfur, a sulfur passivation film is provided on the exposed part of the junction part between an emitter layer and a base layer and after that, an insulating film is applied on the sulfur passivation film.

CONSTITUTION: In a manufacturing process of a heterojunction bipolar transistor, a treatment using (NH4)2Sx is performed immediately after the mesa structure of an HBT is formed by etching and S (surface) is made to adhere on the surface. S atoms respectively bond to Ga, Al and As constituting a semiconductor and unbonded atoms are saturated. As a result, the recombination of carriers on a base-emitter interface is inhibited and even if the size of an element is made fine, a current gain is never reduced. After a treatment using Si is performed, an insulating film 19 consisting of SiO2, SiNx or the like is deposited and after that, the formation of electrodes and the like are performed. It is desirable that (NH4)2Sx(x-1) is used as a compound similar to the (NH4)2Sx and a treatment is performed.