[1] Semiconductor Device Research Center, Semi-conductor Company, Matsushita Electronics Corporation, Takatsuki, Osaka 569-1193, Japan
[2] Kyoto University, Kyoto, Japan
[3] Electronics Research Laboratory, Matsushita Electronics Corporation, Takatsuki, Osaka, Japan
[4] Semiconductor Device Research Center, Semiconductor Company, Matsushita Electronics Corp. T., Osaka, Japan