| 摘要 |
PROBLEM TO BE SOLVED: To provide a bipolar transistor, in which compatibility of a minimum noise exponent reduction by reducing a junction capacity CBE between a base and an emitter, and improvement of high DC current gainβis established. SOLUTION: A non-doped SiGe layer 7 and a non-doped Si layer 6 are arranged between the base layer and the emitter layer in the bipolar transistor, having a base layer constituted of SiGe. At least a part of the Ge composition of the emitter side in the SiGe base layer is made to incline, so that it gradually becomes smaller as going toward the emitter side, and the Ge composition of the non-dope SiGe layer is set to be smaller than Ge composition at the emitter end of the SiGe base layer. The diffusion of boron to the emitter side by heat history is suppressed by arranging the non-dope SiGe layer 7, and it is made smaller than Ge composition at the emitter end of the SiGe base layer so as to reduce CBE, so that by improving the DC current gainβby setting Ge composition at the emitter end of the SiGe base layer thereby it is not less than the prescribed value.
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