Semiconductor device with an enhancement type field effect transistor in which threshold voltage is dependent upon substrate bias voltage

Abstract

An enhancement mode field effect transistor whose operation threshold value varies greatly according to the substrate voltage. This field effect transistor is implemented by substituting the gate electrode of a depression mode field effect transistor for a gate electrode of the conductivity type opposite to that of a channel formation region, or a midgap gate electrode. In a preferred embodiment of the present invention, this field effect transistor is provided between a CMOS structure logic gate and a ground line. As a result, the leak current when the field effect transistor is not operating can be diminished without reducing the operational speed of the logic gate.