ACKNOWLEDGMENT We thank Mr. T. Fukushima, Mr. Y. Kitakoshi, and Mr. R. Ikeda of Kawasaki Microelectornics Incorporation for fruitful discussions in ESD measuremnts, and Dr. Sze Y. Set, Mr. K. Miyaji, Mr. M. Tojo, and Mr. K. Furuki of Alnair Laboratories Corporation for their useful advice and discussions on constructing the optical electric-field probe system.