Low-voltage limitations of memory-rich nano-scale CMOS LSIs

The low-voltage limitations of memory-rich nano-scale CMOS LSIs using bulk CMOS and fully-depleted (FD) SOI devices are described, focusing on CMOS inverter and flip-flop circuits such as six-transistor (6-T) cells in SRAMs and sense amplifiers in DRAMs. The limitations strongly depend on the ever-larger VT variation, especially in SRAM cells and logic gates, and are improved by using the FD-SOI as well as by using repair techniques. Consequently, two possible LSIs are predicted to coexist in the deep-sub-100-nm generation: high-VDD bulk CMOS LSIs for low-cost low-standby-current applications and low-VDD FD-SOI LSIs for low-power applications.