PURPOSE:To obtain a rapid and low-power semiconductor integrated circuit which can be highly integrated, by providing an integrated circuit whose load resistance is connected in series with a thermionic emitting SIT. CONSTITUTION:A thermionic emitting SIT30 having normally-OFF properties has a load resistance 31, an input terminal 20, a grounding terminal 21, an output terminal 22 and a power input 23. When the input is zero and when the thermionic emitting SIT30 is OFF, the level becomes high in the output terminal 22. When the input becomes high, the SIT30 is turned ON and the level becomes low in the output terminal 22. Thus, the SIT30 performs so-called invertor operation. The current flowing through the circuit depends on the value of the load resistance 31. For example, when VDD is 1V and the load resistance is 1kOMEGA, the current is on the order of 1mA. Accordingly, the ON voltage of the thermionic emitting SIT30 becomes very low.