1. Department of Electrical and Computer Engineering Sungkyunkwan University Suwon 16419 Korea
2. Department of Semiconductor and Display Engineering Sungkyunkwan University Suwon 440‐746 Korea
3. Memory Technology Design Team Samsung Electronics Co. Ltd Hwasung 18448 Korea
4. SKKU Advanced Institute of Nanotechnology (SAINT) Sungkyunkwan University Suwon 16419 Korea