1. Research and Development Group, Hitachi, Ltd., 1-280 Higashi-koigakubo, Kokubunji-shi, Tokyo 185-8601, Japan
2. IBM Semiconductor Research and Development Center, 257 County Road, 156, Albany, New York 12205, United States
3. Hitachi High-Technologies Corporation, 882 Ichige, Hitachinaka-shi, Ibaraki-ken 312-8503, Japan
4. IBM Semiconductor Research and Development Center, 2070 Route 52, Hopewell Junction, New York 12533, United States