A gate circuit is constituted by a plurality of logical elements formed on the same P type semiconductor substrate. Each logical element is composed of an N type first region and P type second region formed by double diffusion in one of a plurality of P type isolated islands formed on a P type semiconductor substrate, and an N type isolating region and N type buried region surrounding the islands. The P type second region, N type first region and P type island constitute a first vertical PNP transistor by operating as an emitter, base and collector, respectively, while the N type first region, P type island and N type buried region constitute a second vertical NPN transistor by operating as an emitter, base and collector, respectively. In the plurality of logical elements, a Schottky diode is provided for each input section thereof. Connected to a connection point between an anode of this Schottky diode and a base of the second vertical NPN transistor of one logical element is a collector of that of another logical element. A collector of the second NPN transistor of one logical element constitutes an output section.