Smart body contact for SOI MOSFETs

Summary form only given. SOI MOSFETs exhibit various floating-body effects due to the lack of a contact to the channel region. These effects can show up as a kink in the saturation region of I_DS-V_DS characteristics (higher drive current) and an improvement of the subthreshold slope, or can be as severe as latch-up of the SOI MOSFET at large drain biases. The easiest was to eliminate floating-body effects is to provide a contact to the channel region to deep it at or below the source potential. One problem with providing a body contact is that the increased transistor drive current due to the floating-body effects is lost even in the saturation region, where it may be desirable for high-speed circuit operation. Here, a scheme for providing a smart body contact is presented. This contact acts as a low-resistance channel contact at low gate voltages to keep the transistor off and avoid latch-up. At high-gate voltages, the resistance of this body contact becomes very high and allows the MOSFET channel to float, which increases the drain current due to both MOS body effect and bipolar action