The invention concerns a semiconductor device that can be controlled by the field effect comprising a first zone of a first conduction type, at least one gate electrode of polycristalline silicon, insulated from the first zone, at least one source/emitter region built into the first zone, in which the source/emitter region has a first region of the first conduction type which is built into the first zone and connected to a source/emitter terminal, a second region made of insulating material is disposed beneath the first region and has a greater ground area than the first region.