Current Status of Nonvolatile Semiconductor Memory Technology

In this report, an overview of the current status of nonvolatile semiconductor memory technology is presented. We are reaching the integration limit of flash memories, and many new types of memories to replace conventional flash memories have been proposed. Unlike flash memories, new nonvolatile memories do not require electric charge storing. The possibility of phase-change random access memory (PRAM) or resistive-change RAM (ReRAM) replacing ultrahigh-density NAND flash memories has been discussed; however, there are many issues to overcome, making the replacement difficult. Nonetheless, ferroelectric RAMs (FeRAMs) and MRAMs are gradually penetrating into fields where the shortcomings of flash memories, such as high operating voltage, slow rewriting speed, and limited number of rewrites, make their use inconvenient. For the successful application of new nonvolatile semiconductor memories, they must be practically utilized in new fields in which flash memories are not applicable, and the technology for them must be developed. (C) 2010 The Japan Society of Applied Physics