Self turnoff type semiconductor switching device

Claim 1

A semiconductor switching device comprising: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type adjacent to said first layer; a third semiconductor layer of the first conductivity type adjacent to said second layer such that a junction between said second and third semiconductor layers is partially exposed at an external surface; a fourth semiconductor layer of the second conductivity type adjacent to said third layer such that a junction between said third and fourth semiconductor layers is also partially exposed at said external surface; a first electrode electrically connected to said first layer; a second electrode electrically connected to said fourth layer; a first current control gate portion having a rectifying contact and being formed in an area of said third semiconductor layer, such that said first gate portion responds to a voltage of a first polarity for causing non-conduction of said device between said first and second electrodes and does not change the conduction of said device in response to a voltage of a second polarity; a second voltage control gate portion overlying said junctions between said second and third and between said third and fourth semiconductor layers in said external surface such that said second gate portion causes conduction between said first and second electrodes in response to a voltage of said second polarity and does not change the conduction of said device in response to a voltage of said first polarity; and a common gate terminal for coupling a control voltage signal to said first gate portion and said second gate portion.