Patent ID: 7276744
Filing Date: 2007-10-02
Classification: H01L

Abstract:
1. A semiconductor device with a heterojunction bipolar transistor, comprising: a semiconductor substrate; an emitter contact layer made of an n-type semiconductor formed on the semiconductor substrate; an emitter layer made of another n-type semiconductor formed on the emitter contact layer; a base layer made of a p-type semiconductor formed on the emitter layer, the p-type semiconductor having a forbidden bandgap smaller than a forbidden bandgap of the semiconductor material forming the emitter layer; a collector layer made of still another n-type semiconductor formed on the base layer, the collector layer being narrower than the base layer in a direction parallel to a major face of the semiconductor substrate; a collector contact layer made of yet another n-type semiconductor formed on the collector layer; and an emitter electrode, a base electrode, and a collector electrode, the three electrodes being connected to the emitter contact layer, the base layer, and the collector contact layer, respectively; wherein: the base layer has a plurality of removal portions thereof in a region associated with a peripheral portion of the collector layer; in a stacked semiconductor structural section associated with the removal portions of the base layer, the base layer or the emitter layer or the emitter contact layer does not exist or neither of the latter two layers exists; between, of the plural removal portions of the base layer, adjacent first and second removal portions thereof, the base layer exists and the emitter layer or the emitter contact layer does not exist or neither of the latter two layers exists; at an external base layer associated with a position external to the removal portions of the base layer, the base layer, the emitter layer, and the emitter contact layer exist in order for the external base layer to have a columnar structure; and a base-emitter junction area is smaller than a collector-base junction area.