| 摘要 |
PROBLEM TO BE SOLVED: To provide an SiGe heterojunction bipolar transistor having a higher cut-off frequency. SOLUTION: There are provided a process, where on a substrate surface with an n-type first semiconductor layer being exposed, a second semiconductor layer whose band gap is narrower than that of the first semiconductor layer and a third semiconductor layer whose band gap is wider than that of the second semiconductor layer are laminated, a process where p-type impurity is added from the substrate surface to form a p-type impurity added region which is shallower than the second semiconductor layer, a process where an insulating layer which covers the third semiconductor layer surface is formed, a process where the insulating layer is provided with an opening where the third semiconductor layer surface is exposed by its bottom part, and a process where an n-type impurity is added from the bottom-part exposed surface through the opening to form an emitter region chiefly in the third semiconductor layer. Here, the bottom part of base region which is a p-type impurity added region remain in the semiconductor layer, even at the completion of emitter-region formation.
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