Patent ID: 7202515
Filing Date: 2007-04-10
Classification: H01L

Abstract:
1. A hetero junction bipolar transistor, comprising: a collector region layer; a base layer formed on the collector region layer; a base protection layer formed on the base layer and containing In; a base electrode formed on a part of the base protection layer; an emitter layer formed on another part of the base protection layer and forming a heterojunction with the base layer and containing Ga and As; an emitter contact layer formed on the emitter layer and containing In; and an emitter electrode formed above the emitter contact layer and including a WSi layer and other metal layers, wherein a side surface of the emitter layer is shaped by dry etching and is substantially perpendicular to a top surface of the emitter layer, and a width of the emitter layer is narrower than that of the emitter contact layer.