Memory Devices: Part II – Non-Volatile Memories

This article illustrates the basic concepts underlying the operation of non-volatile memories (NVM). After a classification of NVMs based on their functional properties with respect to the programming and erasing operations, the treatment addresses the structure, operation principles, circuit organization and reliability issues of read-only memories (ROM), electrically programmable read-only memories (EPROM), electrically programmable and erasable read-only memories (EEPROM) and flash memories, including both the NOR and NAND organizations. A final section is devoted to non-conventional memories, including magnetic, ferroelectric and phase-change memories, which are still in an early development stage.