High frequency characteristics of dynamic threshold-voltage MOSFET (DTMOS)under ultra-low supply voltage

Dynamic Threshold-Voltage MOSFETs (DTMOS) in which the body is connected to the gate provide extremely high transconductance for supply voltages as lo w as under 0.7 V. This is because the forward body-source bias lowers the t hreshold voltage, which results in large gate drive and large drain current . This paper describes the high frequency characteristics of DTMOS for the first time. The DTMOS we analyzed has a small parasitic resistance due to e mploying optimized Co salicide technology. It also has a small parasitic ca pacitance due to a reduction in the overlapping region between the gate and drain, which is achieved by employing gate poly-Si oxidation prior to LDD implantation. We obtained an F-t of 78 GHz and an F-max of 37 GHz for a 0.1 -mu m-L-eff DTMOS even at a supply voltage of 0.7 V. We also observed an F- max enhancement by 1.5 times for a 0.12-mu m-L-eff DTMOS compared to a conv entional SOI MOSFET, which we attributed to high transconductance and large output resistance. The DTMOS can be considered as the most promising devic e for low-power RF LSIs.