PURPOSE: To realize a high gain by a method wherein an emitter region for a bipolar transistor is constituted of the following: a first region in which the lattice of a semiconductor crystal is contracted; and a second region in which the lattice of the semiconductor crystal is not contracted.
CONSTITUTION: Phosphorus ions are implanted by using an ion implantation method; after that, germanium ions are implanted and annealed. At this time, a band gap is narrowed in an emitter region 12 due to a lattice contraction. However, impurity atoms whose covalent bond radius is larger than that of silicon atoms are added to an emitter region 11. As a result, a lattice strain is compensated, and the band gap is not narrowed due to the lattice contraction. As a result, a wide gap emitter such as a heterojunction is formed. Thereby, even when a base is made as a thin layer and a base concentration is made high in order to make the speed of a transistor high, it is possible to obtain a high current gain.
NANBA MITSUO
KOBAYASHI TAKASHI
NAKAMURA TORU
