The present invention relates to a
semiconductor layer applicable to a hetero-junction bipolar
transistor, a forming method thereof, and a
semiconductor device and a manufacturing method thereof, for example. The
semiconductor layer and the forming method thereof according to the present invention includes a first SiGe film or SiGeC film containing Ge of which the concentration become equal to a
thermal expansion coefficient of
silicon oxide and a second SiGe film or SiGeC film formed on the first film. In a
semiconductor device according to the present invention and a manufacturing method thereof, first and second
layers are laminated on an
oxide film having an opening, and the first layer has the substantially same
thermal expansion coefficient as that of the
oxide film and has a
thermal expansion coefficient different from that of the second layer. Thus, a stress that is caused by a difference between the thermal expansion coefficients becomes difficult to occur in the laminated film, and hence the occurrence of misfit
dislocation can be suppressed. Thus, the present invention is suitable as the application to a hetero-junction bipolar
transistor.