publication_number US 2003155631 A1 abstract a vertical bipolar transistor has a j fet incorporated in an epitaxial layer the pinch off voltage of the j fet is less than the collector emitter breakdown voltage of a bipolar transistor without the j fet this results in a considerable increase in the collector emitter breakdown voltage up to 30 v or more being possible without having to except limitations with regard to dielectric strength and on resistivity application_number US 36700503 A description in the figures mutually corresponding structural parts are provided with the same reference symbols referring now to the figures of the drawing in detail and first particularly to fig3 thereof there is shown the construction of a conventional vertical npn bipolar transistor in bcd technology bcd bipolar u2212 cmos u2212 dmos the npn bipolar transistor has on a p u2212 doped semiconductor substrate 1 made of silicon for example an n doped epitaxial layer 2 made likewise of silicon for example situated in a region between the semiconductor substrate 1 and the epitaxial layer 2 is an nor n doped buried layer 3 that acts as a collector contact and is at any rate doped more highly than the epitaxial layer 2 the buried layer 3 is connected via an n doped terminal region 4 to a collector electrode 6 provided on a surface 5 of the epitaxial layer 2 the doping concentration of the terminal region 4 is expediently of the same order of magnitude as the doping concentration of the buried layer 3 in the region above the buried layer 3 a p doped base zone 7 is situated at a distance from the latter in the surface 5 of the epitaxial layer 2 which base zone 7 is contact connected to a base.