| 摘要 |
A semiconductor device with HBT that enables the cutoff frequency of the HBT to be restrained from lowering at higher collector current levels. The HBT has an emitter region, a SiGe base region, and first and second SiGe collector regions. The first collector region is adjacent to the base region. The base region has a first distribution of Ge concentration graded as a function of depth. The Ge concentration of the first distribution increases at a first gradient as a function of depth from a base-emitter junction to a base-collector junction. The first and second collector regions have second and third distributions of Ge concentration graded as a function of depth. A minimum Ge concentration of the second distribution is not lower than a maximum Ge concentration of the third distribution. In the vicinity of an interface of the first and second collector regions, Ge concentration of the second distribution decreases at a second gradient as a function of depth to the interface, Ge concentration of the third distribution decreases at a third gradient smaller than the second gradient as a function of depth from the interface toward an opposite end of the interface.
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