Abstract: The invention relates to a semiconductor device comprising a semiconductor body (10) including, for example, a p-type substrate (11) and a PNP bipolar transistor having a collector (1), a base (2) and an emitter (3), which are each provided with a connection conductor (7, 8, 9). One or more of the connection conductors (7, 8, 9) extend over a part of an insulating layer (20) which covers the body (10) which contains, below said insulating layer (20), a further semiconductor region (4) of a conductivity type opposite to that of the substrate (11). A disadvantage of the known device is that it is less suitable for certain applications, such as power amplification. In a device according to the invention, a sub-region (4b) of the further semiconductor region which borders on the substrate (11) is provided with a higher doping concentration than the remainder (4a) of the further semiconductor region (4).