CMOS INVERTER CIRCUIT AND ITS DESIGN METHOD

PURPOSE:To reduce deterioration due to hot carrier to the utmost by using simulation of the circuit and its reliability and taking the capacitive coupling into account. CONSTITUTION:In the inverter in which a predetermined voltage is applied to a gate 308 of an inserted NMOSFET, an optimum voltage is selected by using the result of the hot carrier simulation by taking an actual waveform and capacitive coupling into account and the deterioration is minimized. For example, a gate voltage is selected between 0.81Vcc and 0.93Vcc to set the service life of the device within a range smaller than the optimum value by one digit order. In the case of the inverter in which the gate 308 of an inserted MOSFET 307 is connected to the input, a depletion device is adopted for an inserted NMOSFET 307. For example, when a nominal threshold voltage of a driver device 105 is 0.72V, the service life of the device is selected within a range shorter than the optimum value by one digit order by selecting a threshold voltage of the inserted MOSFET 307 to be a voltage between -1.0V and -0.81V.