The present inventive concept relates to a non-volatile memory devices including an array of non-volatile memory cells. More particularly, the inventive concept relates to non-volatile memory cell arrays having erase markers and methods of operating same.
Semiconductor memory devices may be classified as volatile and non-volatile in their operating characteristics. Volatile memory devices are generally able to perform read/write operations quickly, but lose stored data in the absence of applied power. On the other hand, non-volatile memory devices are able to retain stored data in the absence of applied power. Current examples of the non-volatile memory devices include the mask read-only memory (MROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.
Extensive ongoing research is focused on emerging non-volatile memory devices that are capable of storing data using material exhibiting variable resistance. Examples of memory devices using variable resistance include the phase change random access memory (PRAM), resistive random access memory (RRAM), magnetic random access memory (MRAM), etc.
Certain volatile memory devices like the dynamic RAM (DRAM) as well as certain non-volatile memory devices like flash EEPROM store data in relation to an amount of electrical charge accumulated within the constituent memory cells (i.e., in relation to a number of “charge states”). In contrast, semiconductor memory devices using a variable resistance material store data in relation to a level of resistance exhibited by the constituent memory cells (i.e., in relation to a number of “resistance states”). The PRAM stores data in relation to a number of material state for a chalcogenide alloy, the RRAM stores data in relation to the resistance exhibited by a variable resistance material, the MRAM stores data in relation to the resistance exhibited by a magnetic tunnel junction (MTJ) thin film as defined by a magnetization state of a ferromagnetic substance.
Many newer non-volatile memory device technologies, like the PRAM, RRAM and MRAM, offer promising performance advantages and system utilities over older non-volatile memory devices. Yet, multiple challenges are presented by these technologies. For example, certain non-volatile memory devices require a considerable amount of time to erase data. It is a common requirement within many non-volatile memory devices that data be erased on a block-by-block basis, and erasing an entire block of non-volatile memory cells takes a significant amount of time, thereby slowing overall memory system performance.