Bipolar transistor which can be controlled by field effect and method for producing the same

The method of forming an insulated gate bipolar transistor comprising the steps of:

• forming, at the top surface of a semiconductive substrate that is doped to be of one conductivity type for serving as the inner zone of the transistor, at least one emitter zone of the one conductivity type with each emitter enclosed within a separate base zone of the opposite conductivity type;
• forming, at the top surface of the semiconductive substrate, a plurality of gate electrodes for inducing channels at the top surface of the substrate for the flow of charge carriers between the emitter zones and the bulk of the substrate by way of the base zones;
• forming, at the bottom surface of the substrate, a polycrystalline field stop zone layer of the one conductivity type but more heavily doped than the bulk of the substrate;
• and forming, at the surface of the field stop layer a collector layer and a collector electrode for injecting minority carriers into the bulk of the substrate, the doping in the collector layer being higher than in the field stop zone layer and of the opposite conductivity type.