PURPOSE: To ensure a wide range of an operating current property and to enable a high speed operation even with a low voltage on an insulating substrate large in area by a method wherein a collector, a base, and a emitter region are formed of a selective epitaxial growth layer which is made to grow through a silicon seed layer as a seed crystal which crystallized on an insulating substrate by the irradiation with energy rays.

CONSTITUTION: A collector region 19 is composed of an n-type germanium layer 3, a base region 20 is formed of a P+-type germanium layer 4, and an emitter region 21 consists of an n+-type silicon layer 8. These three layers are the films which are formed in layers inside a trench through a selective epitaxial growth method making use of an n+-type silicon layer 2 under these three layers as a seed crystal, where the trench is formed of an insulator layer 5. The n+-type silicon seed layer 2, serving as a seed crystal, is fused and crystallized by irradiating it with laser rays. When a bipolar transistor provided with such a heterojunction in operation, electrons are made to flow at a high speed through the following regions in this order: an emitter electrode 9; the emitter region 21; the base region 20; the collector region 19; and the n+-type silicon seed layer 2.