The present disclosure relates to a method for manufacturing a bipolar transistor. The method forms a trench to isolate a first region from a second region in a semiconductor wafer, and to isolate these regions from the rest of the wafer. The method forms first P-doped well in the second region and produces a collector region of second and third wells by a P doping in the first region. The second well is in contact with the first well below the trench. The method also produces an N-doped base well on the collector region and, at the wafer surface, and forms a CMOS transistor gate on the first region and delimiting a third region and a fourth region. The method also forms a P+-doped collector contact region in the first well, forms a P+ doped emitter region in the third region, and forms an N+-doped base contact region in the fourth region.