| 摘要 |
PURPOSE:To prevent the destruction of a gate film and the lowering of a switching speed by inserting a depletion-type MOSFET between the external terminal and a protected MOSFET. CONSTITUTION:N-type source drain 2 and electrode 5 are provided on P<->-type substrate 1 and gate insulating film 4 respectively to form a FET, and protection devices Q0 and Q0' are completed by providing N channel 8 between N-type drain 6 and source 7 and providing gate electrode 10 through insulating film 9, and p layer 12 is formed and is used as a resistance as well as a diode after forming N layer 11 for protecting film 9. The surface is covered with insulating gilm 13, and electrodes are formed selectively. In this constitution, each external terminal is connected to the drain of depletion-type FET even if external terminals provided in the case are independent respectively, and an on-state is held normally across the drain and the source unless a proper negative voltage is applied to the protection gate terminal. As a result, even if the external terminal is charged with a high voltage, the external terminal is short-circuited to the substrate immediately to prevent the destruction of the gate film. |
