To provide a semiconductor integrated circuit technology for reducing a leakage current by meticulously interrupting power of part of a function block in operations.

In the function block 1 including a clock tree, a combination circuit, flip-flops 7, 8, and a power switch 9, when clocks applied to the flip-flops 7, 8 are stopped, power of a part region 11 of the combination circuit and of a part circuit of the flip-flops 7, 8 is interrupted without losing contents of the flip-flops 7, 8. Using a signal resulting from processing a control signal of a higher-order side of the clock tree for a control signal of the power switch 9 can execute a wide variety of power controls for the combination circuit and the flip-flops 7, 8 while suppressing timing deterioration more in comparison with absence of the power control. When the clocks applied to the flip-flops 7, 8 are restarted, power is supplied to the part circuit of the combination circuit and the flip-flops 7, 8 and the operation is resumed.

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