BIPOLAR TRANSISTOR CAPABLE OF BEING INTEGRATED

The basis of the invention is a bipolar transistor structure suitable for ICs as described in German Offenlegungsschrift 3,029,553. For this structure it is essential that the base zone has a larger lateral cross sectional area than the buried zone (buried layer) situated beneath it at a distance and serving to reduce the collector spreading resistance. In addition, it should extend laterally beyond the buried zone at all points along its edge. These measures result in a parasitic junction field-effect transistor which ensures that the transistor acquires an appreciable increase in its breakdown voltage. The object of the invention is to achieve a yet further increase in the breakdown voltage. For this purpose, according to the invention, the doping of the epitaxial semiconductor layer accommodating the transistor with the exception of the buried zone and, consequently, the background doping as well as the substrate doping are matched to one another in a manner such that, because of an operating voltage which is already markedly below the CE breakdown voltage, an interaction is produced between the space charge zones which, on the one hand, emanate from the base-collector junction and, on the other hand, from the substrate-collector junction during the operation of the transistor.