JPS6436060A - Static electricity protective device of mis integrated circuit - Google Patents

Abstract

PURPOSE:To improve protection capacity of a gate insulation film and to obtain an integrated circuit of high reliability, by supplying a gate potential of a MIS transistor, which functions as a protective element for static electricity and is non-conductive on its stationary state, through a MIS transistor which is of the same conduction type and conductive on its stationary state. CONSTITUTION:Positive static electricity is applied between a terminal 51 and an earth power source, and so a high electrical field is temporarily applied between a drain and a gate of an N channel MIS transistor 1-2. Then an alternating current is made to flow through a coupling capacitor connected between the drain and the gate, and this current is released to the earth power source through an N channel MIS transistor 2-2 so that discharge is performed. The betavalues of the respective N channel MIS transistors are made to be beta1-2 and beta2-2, and the set relation is made beta2-2<=beta1-2/10 or so. Thereupon, an on resistance during discharge is made sufficiently high and so an electric field between the gate and the drain can be suppressed to be very low. The design of the resistance value is facilitated so that this integrated circuit can be manufactured with high protection capacity in its gate insulation film.