Abstract: An insulated gate turn-off (IGTO) device has a layered structure including a p+ layer (e.g., a substrate), an n-type layer, a p-type layer (which may be a p-well), n+ regions formed in the surface of the p-type layer, and insulated planar gates over the p-type layer between the n+ regions. The layered structure forms vertical NPN and PNP transistors. The p-type layer forms the base of the NPN transistor. When the gates are sufficiently positively biased, the underlying p-type layer inverts to reduce the width of the base to increase the beta of the NPN transistor. This causes the product of the betas of the NPN and PNP transistors to exceed one, and the device becomes fully conductive. When the gate voltage is removed, the base width increases such that the product of the betas is less than one, and the device shuts off. No latch-up occurs in normal operation.