1. a Memory LSI Resarch & Development Center , Toshiba Corp. Semiconductor Company , 8, Shinsugita-cho, Isogo-ku, Yokohama, 235-8523, Japan
2. b Corporate Manufacturing Engineering Center , Toshiba Corp. , 33, Shinisogo-cho, Isogo-ku, Yokohama, 235-0017, Japan
3. c Process Resarch & Development Center , Toshiba Corp. Semiconductor Company , 8, Shinsugita-cho, Isogo-ku, Yokohama, 235-8523, Japan