| 摘要 |
PURPOSE: To reduce low frequency noise in base-emitter junction space charge region by a structure wherein an emitter region has a mesa part and a shelf part thinner than the mesa part with the mesa part being spread over a part of a base region on the outside of the mesa part. CONSTITUTION: A collector area 3 is formed epitaxially on a subcollector 1. Similarly, a base layer 5 is formed on the collector layer 3 followed by formation of an emitter layer 7 and an N type layer 8. Subsequently, an emitter metal 9 is deposited partially on the surface of the N type layer 8 and used as a mask for forming a shelf part 11 and a mesa part 13. Finally, a resist layer 15 on the shelf part 11 is removed by etching while leaving a part thereof until the base layer 5 is reached. Consequently, the shelf part 11 of emitter is spread on the surface of the base and noise characteristics can be improved for both low frequency and high frequency.
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