Back-gated CMOS on SOIAS for dynamic threshold voltage control

The simultaneous reduction of power supply and threshold voltages for low-power design without suffering performance losses will eventually reach the limit of diminishing returns as static leakage power dissipation becomes a significant portion of the total power consumption. This is especially acute in systems that are idling most of the time. In order to meet the opposing requirements of high performance at reduced power supply voltage and low-static leakage power during idle periods, a dynamic threshold voltage control scheme is proposed. A novel Silicon-On-Insulator (SOI)-based technology called Silicon-On-Insulator-with-Active-Substrate (SOIAS) was developed whereby a back-gate is used to control the threshold voltage of the front-gate; this concept was demonstrated on a selectively scaled CMOS process implementing discrete devices and ring oscillators. For a 250 mV switch in threshold voltage, a reduction of 3-4 decades in subthreshold leakage current was measured.