Inventive concepts described herein relate to a semiconductor memory device, and more particularly, to a nonvolatile memory device and/or a control method thereof.
Semiconductor memory devices may be characterized as volatile or nonvolatile. A volatile semiconductor memory device may perform read and write operations in a high speed, while data stored therein may be lost upon removal of power from the device. A nonvolatile semiconductor memory device may retain data stored therein even upon removal of power from the device. Accordingly, a nonvolatile semiconductor memory device may be used to store data which must be retained regardless of whether the device is powered.
A flash memory device may be a typical nonvolatile semiconductor memory device. The flash memory device may be used as a voice and image data storing medium for information appliances such as a computer, a cellular phone, a PDA, a digital camera, a camcorder, a voice recorder, an MP3 player, a handheld PC, a game machine, a facsimile, a scanner, a printer, and the like.
In recent years, research has been conducted on nonvolatile memory devices where memory cells are stacked three-dimensionally to improve a degree of integration of the devices. Such a nonvolatile memory device may be referred to as a vertical NAND flash memory device or a three-dimensional nonvolatile memory device. In the three-dimensional nonvolatile memory device, word lines may be stacked in a direction perpendicular to a substrate. Cell strings may be constituted by forming pillars to penetrate the stacked word lines.
The pillars may be disposed in a zigzag shape to improve efficiency of space arrangement. This structure may cause irregular driving characteristics of strings. Thus, a technique of solving such a problem of the three-dimensional nonvolatile memory device is desired.