The inventive concepts described herein relate to nonvolatile memory devices, and more particularly to methods of programming and reading nonvolatile memory devices.
Semiconductor memory devices may be classified into volatile semiconductor memory devices and nonvolatile semiconductor memory devices. While volatile semiconductor memory devices may perform read and write operations at high speed, contents stored therein may be lost when the devices are powered-off. Nonvolatile semiconductor memory devices may retain contents stored therein even when powered-off. For this reason, nonvolatile semiconductor memory devices are typically used to store contents that are to be retained regardless of whether the devices are powered on or off.
Examples of nonvolatile semiconductor memory devices include mask read-only memories (MROMs), programmable ROMs (PROMs), erasable programmable ROMs (EPROMs), electrically erasable programmable ROMs (EEPROMs), or the like.
A flash memory device is a typical nonvolatile memory device. Flash memory devices are widely used as voice and image storing mediums of electronic apparatuses such as computers, cellular phones, personal digital assistants (PDAs), digital cameras, camcorders, voice recorders, MP3 players, handheld PCs, game machines, facsimiles, scanners, printers, or the like.
As highly integrated memory devices have recently become increasingly necessary, multi-bit memory devices capable of storing multi-bit data in memory cells have become more common. As the operation speed of electronic devices increase, the operation speed of memory devices must also increase. However, programming speed and reading speed of flash memories are generally low.