Low-voltage embedded RAMs in the nanometer era

Low-voltage nanometer-scale embedded RAM cells are described. First, low-voltage RAM cells are compared in terms of cell size, threshold voltage for MOS transistor, and signal charge. Second, the solution for 6T and 4T SRAM cells to widen the voltage margin are investigated, especially the advantages with a back-gate controlled thin buried-oxide fully-depleted SOI are presented. Then, DRAM approach with a novel twin- cell is discussed in terms of improving the retention time and low-voltage operation. These low-voltage cell technologies are the promising candidates for future embedded RAMs.