A 1.9-/spl mu/m/sup 2/ loadless CMOS four-transistor SRAM cell in a 0.18-/spl mu/m logic technology

We present a loadless CMOS four-transistor cell for very high-density embedded SRAM applications. Using 0.18-/spl mu/m CMOS technology, the memory cell size is 1.9344 /spl mu/m/sup 2/ (1.04 /spl mu/m/spl times/1.86 /spl mu/m), which is 35% smaller than a six-transistor cell using the same design rule. The newly developed CMOS 4T cell operates with high stability at 1.8 V, even though its designed cell ratio is 1.0 to minimize the area. A pair of pMOS transfer transistors is used to store and retain full-swing signals in the cell without a refresh cycle. The fabrication process is fully compatible with high performance CMOS logic technologies, because there is no need to integrate a poly-Si resistor or a TFT load.