Memory or storage devices continue to be of great importance in a variety of electrical and computer systems, as well as a variety of other applications. Memory devices can take a variety of forms including, for example, non-volatile memory devices (e.g., flash memory devices, ROM, PROM, EPROM, EEPROM, etc.) and volatile memory devices (e.g., random access memory or RAM, DRAM, SRAM, SDRAM, etc.).
Although many useful memory/storage devices already exist, the evolution of a variety of technologies (including, for example, computer technologies) continues to drive a need for improved memory/storage devices that are improved on a number of counts. First, there continues to be a need for memory/storage devices capable of storing ever-greater amounts of data and information. At the same time, there also continues to be a need for memory or storage devices that are of increasingly small size, and so there continues to be a need for memory/storage devices with higher packing densities.
In addition to the needs for ever smaller memory/storage devices having ever greater data storage capabilities, there also continues to be a need for memory/storage devices that are capable of storing (and allowing for the retrieval) of stored data at increasingly rapid rates. Further, there continues to be a need for memory/storage devices that are capable of operating using reduced amounts of power, and that are capable of operating with less heat dissipation.
Existing state of the art non-volatile memory technology (for example, flash memory devices employing field effect transistor technologies) faces enormous obstacles in further scaling down. For example, planar flash memory technology based on silicon field effect transistors faces obstacles to further miniaturization. Scaling of the tunneling oxide used in these memory cells is complicated by the incompatible requirements of high programming current and minimal leakage current—that is, miniaturization results in incompatible requirements of high programming current and low leakage currents. As devices are scaled down/made smaller, increased current density or increased programming currents/unit area are necessary to write information onto the devices. However, increased current results in an increased possibility for the current to leak (leakage currents), which means higher static power dissipation which is undesirable, again. Further, the increased voltage needed for hot electron injection is an additional problem. This is a problem particularly during the programming part of the flash memory operation
Indeed, while the basic tunneling mechanism used in flash memory is useful and attractive, it is widely recognized that alternative materials and new device architectures are needed in order to achieve further advances in non-volatile memory (see, for example, the discussion provided in “Flash Memory Scaling”, Emerging Solid State Memory Technologies, MRS Bulletin, Volume 29, November, 2004, which is hereby incorporated by reference herein).
It would therefore be advantageous if improved memory devices and or methods of operating memory devices were developed, and/or new technologies were developed for fabricating such improved memory devices. It would further be advantageous if, in at least some embodiments, such improved memory devices had greater memory capacity, took on a smaller size, and/or had greater packing densities than conventional memory devices. It would additionally be advantageous if, in at least some embodiments, such improved memory devices could operate at greater speeds, with less power and heat dissipation, than conventional memory devices. Such advantages would be desirable in a variety of different types of memory devices including, for example, flash memory devices.