It has been fifty years since the invention of the bipolar transistor, more than forty years since the invention of the integrated-circuit (I C) technology, and more than thirty-five years since the invention of the MOSFET. During this time, there has been a tremendous and steady progress in the development of the IC technology with a rapid expansion of the IC industry. One distinct characteristic in the evolution ofthe IC technology is that the physical feature sizes of the transistors are reduced continually over time as the lithography technologies used to define these features become available. For almost thirty years now, the minimum lithography feature size used in IC manufacturing has been reduced at a rate of 0. 7 x every three years. In 1997, the leading-edge IC products have a minimum feature size of 0.25 ~-tm.