1-V power supply high-speed low-power digital circuit technology with 0.5-mu m multithreshold-voltage CMOS (MTCMOS) is proposed, This technology features both low-threshold voltage and high-threshold voltage MOSFET's in a single LSI. The low-threshold voltage MOSFET's enhance speed performance at a low supply voltage of 1 V or less, while the high-threshold voltage MOSFET's suppress the stand-by leakage current during the sleep period, This technology has brought about logic gate characteristics of a 1.7-ns propagation delay time and 0.3-mu-W/MHz/gate power dissipation with a standard load. In addition, an MTCMOS standard cell library has been developed so that conventional CAD tools can be used to lay out low-voltage LSI's, To demonstrate MTCMOS's effectiveness, a PLL LSI based on standard cells was designed as a carrying vehicle, 18-MHz operation at 1 V was achieved using a 0.5-mu m CMOS process.