An electronic device includes a semiconductor memory. The semiconductor memory includes a word line, a bit line, and a memory cell coupled to and disposed between the word line and the bit line, the memory cell including a variable resistance layer that remains in an amorphous state regardless of a value of data stored in the memory cell. In a reset operation, the memory cell is programmed to a high-resistance amorphous state by applying, to the memory cell, a sub-threshold voltage that is greater than 0.7 time of a threshold voltage of the memory cell and is smaller than 0.95 time of the threshold voltage.