| 摘要 |
Provided is a method of measuring threshold voltages in a NAND flash memory device. In the method, a test voltage is applied to a wordline of selected memory cells to measure a distribution profile of threshold voltages of memory cells. A voltage summing up a pass voltage and an operation voltage is applied to wordlines of deselected cells. The operation voltage is applied to a well and a common source line. A voltage summing up a precharge voltage and the operation voltage is applied to a bitline. After then, a voltage variation on the bitline can be detected to measure a threshold voltage of a memory cell. A negative threshold voltage can be measured by applying a positive voltage with reference to a voltage, as the threshold voltage of the memory cell, set by subtracting the operation voltage from the test voltage in accordance with the bitline voltage variation.
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