Insulated-gate field-effect transistor (IGFET) with injector zone

IGFET assembly, comprising a semiconductor substrate of a given first conductivity type having first and second surfaces, an IGFET having at least one channel zone of a second conductivity type opposite said first given conductivity type embedded in said first surface of said substrate, a source zone of said first conductivity type embedded planar in said channel zone, a drain zone adjacent said first surface of said substrate, a drain electrode connected to said second surface of said substrate, an insulating layer disposed on said first surface of said substrate, at least one gate electrode disposed on said insulating layer, a bipolar transistor having at least one base zone of said second conductivity type embedded in said first surface of said substrate, and an emitter zone of said first conductivity type embedded in said base zone, said emitter zone having a heavier doping than said base zone, said base zone including first parts and second parts thereof emerging to said first surface of said substrate, said drain zone having parts thereof emerging to said first surface of said substrate, and first parts of said base zone and said parts of said drain zone emerging to said first surface of said substrate being covered by said gate electrode, an auxiliary FET disposed in said substrate and having a source zone, a channel zone and a drain zone, said drain zone and said channel zone having parts thereof emerging to said first surface of said substrate, said channel zone of said auxiliary FET being electrically connected to said base zone, a floating contact contacting said source zone and said channel zone of said auxiliary FET, a further gate electrode disposed on said insulating layer and covering said second parts of said base zone and said part of said channel zone of said auxiliary FET emerging to said first surface of said substrate, and said base zone having a surface and having a doping, at least at said surface thereof, forming channels in said surface of said base zone connecting said drain zones of said IGFET and of said auxiliary FET to said emitter zone when a voltage is present switching said IGFET into conduction.