In semiconductor-device fabrication processes, lithography technology is used to print circuit patterns on semiconductor wafers. The remarkable miniaturization of semiconductor devices has been made possible only because of the continuous progress in lithography technology. However, for the trend of ever-increasing miniaturization to continue a breakthrough in lithography technology is now needed. This book describes advanced techniques under development in Japan and elsewhere that represent the key to future semiconductor-device fabrication. The background to developments in lithography technology, trends in ULSI technology and future prospects are reviewed, and the requirements that future lithography technology must meet are described. Several important lithography methods, such as deep UV lithography, X-ray lithography, electron-beam lithography, and focused ion-beam lithography are described in detail by experts in each area. The principles underlying each of these methods are illustrated at the beginning of each chapter to help the reader understand the basis of the different approaches.