an insulated gate control thyristor including an n - type base region , an insulating layer , gates formed on the insulating layer , first and second windows formed in the insulating layer , p - type emitter layers and n - type cathode layers diffused into the base region from the first windows , and p - type collector layers diffused into the base region from the second windows . the emitter layer and the collector layer are disposed in close proximity to each other under the gate so that a channel is formed which is conducted when the thyristor is turned off . the turn - off of the thyristor speeds up and becomes reliable , and the quality control of the process steps for fabricating the thyristor becomes easier .