1. a Department of Electrical Engineering , Korea Advanced Institute of Science and Technology , 373–1, Kusong-dong, Yusong-gu, Taejon, 305–701, Korea
2. b Micro-Electronics Technology Laboratory, ETRI , 161, Kajong-dong, Yusong-gu, Taejon, 305–600, Korea
3. c TD Team, Semiconductor R&D Center, Samsung Electronics Co. , San#24 Nongseo-ri, Kiheung-eup Yongin-city, Kyunggi-do, 449–771, Korea