| 摘要 |
A multi-bit operation method of a phase change memory device is provided to store at least two bits data and to obtain four states of a phase change resistor by changing the direction of pulse current/voltage, thereby improving reliability of a program operation of the phase change memory device. According to a multi-bit operation method of a phase change memory device including a phase change resistor, and first and second electrodes connected to both ends of the phase change resistor, a program step changes the resistance value of the phase change resistor into at least four states by applying an electrical signal from/to the first electrode to/from the second electrode. A read step reads the resistance value of the programmed phase change resistor by applying an electrical signal in a random direction between the first electrode and the second electrode.
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