ABSTRACT
USUM cells are all nonvolatile memory cells. USUM cells operating within the framework of the first approach are defined and labeled by the associated active device and designed to functionally replace a conventional memory exclusively such as SRAM or DRAM or NROM or NAND. The USUM version of such cell was proposed to be a vertically integrated gated thyristor cell in bulk implementation featuring two word lines, in principle similar to the previously discussed diode cell, while the SOI implementation is a single word line based on floating body-induced charge trapping similar to that discussed in the diode version of the USUM cell. The USUM cells are direct tunnel memory-based cells and employ enhanced direct tunneling modes for higher performance charge transport and enhanced charge trapping/storage modes combined with effective charge-retention mode for nonvolatility and MLC capability. These memory cells are generalized as charge trapping direct tunnel memory (CT-DTM) cells.
