A semiconductor integrated circuit, comprises a first reference voltage line; a second reference voltage line; a plurality of single logic circuits each including a plurality of transistors; a first switch having a first transistor provided between said first reference voltage line and said logic circuits, said first transistor having a higher threshold voltage than that of transistors in the logic circuits; and a second switch having a second transistor provided a between said second transistor having a higher threshold voltage than that of transistors in the logic circuits, said first and second switches being turned on when at least one of said single logic circuits is in operation, while said first and second switches being turned off when all of said single logic circuits are in standby state.