Bipolar transistor controlled by field effect by means of an isolated gate

Claim 1

A semiconductor structure of the bipolar conduction type controlled by an isolated gate which is adapted to render said structure selectively conductive or to block the same, comprising : a semiconductor substrate doped with an impurity having a conductivity of a first type, said substrate constituting an emitter area of a vertical bipolar transistor formed in said structure, an emitter contact electrically connected to said substrate, an epitaxial layer slightly doped with an impurity having a conductivity of a second type opposite to the conductivity of said first type, which epitaxial layer covers said substrate and constitutes a base area of said bipolar transistor, a collector area having a conductivity of said first type and strongly doped from the surface of said epitaxial layer in its major portion, said collector area being surrounded by an area wherein said epitaxial layer of second type conductivity is exposed and said collector area being covered on the major portion of its surface with a collector contact; a source area constituted by a zone doped from the surface of said epitaxial layer with an impurity having a conduction of said second type, said doped zone being included within said collector area and extending along a border thereof while exposing an interval between said area and said zone, a thin isolating layer covering said interval, and a conductive layer covering said thin isolating layer, so as to constitute the control gate of said structure, and a resistive source access zone connected, on the one hand, to said source area and, on the other hand, to said collector contact, the resistance of said zone being sufficiently high to prevent the junction constituted between the source area and the collector area from being rendered conductive when a current passes through the collector.