A monolithically integrated light-activated thyristor in an n-p-n-p-n-p sequence consists of a four-layered thyristor structure and an embedded back-biased PN junction structure as a turn-off switching diode. The turn-off switching diode is formed through structured doping processes and/or depositions on a single semiconductor wafer so that it is integrated monolithically without any external device or semiconductor materials. The thyristor can be switching on and off optically by two discrete light beams illuminated on separated openings of electrodes on the top surface of a semiconductor body. The carrier injection of the turning on process is achieved by illuminating the bulk of the thyristor with a high level light through the first aperture over the cathode to create high density charge carriers serving as the gate current injection and to electrically short the emitter and drift layer. The switching off of the thyristor is achieved by shorting the base layer and the cathode layer by illuminating the embedded back-biased PN junction of the TURN-OFF switching diode. The patterned doping profile and the interconnect between the emitter and the base region of the light activated thyristor makes possible a monolithic and/or planar integrated fabrication of the semiconductor switching device on a single semiconductor wafer via the standard semiconductor fabrication process.