Semiconductors lie at the heart of some of the most important industries and technologies of the twentieth century. The complexity of silicon integrated circuits is increasing considerably because of the continuous dimensional shrinkage to improve efficiency and functionality. This evolution in design rules poses real challenges for the materials scientists and processing engineers. Materials, defects and processing now have to be understood in their totality. World experts discuss, in this volume, the crucial issues facing lithography, ion implication and plasma processing, metallization and insulating layer quality, and crystal growth. Particular emphasis is placed upon silicon, but compound semiconductors and photonic materials are also highlighted. The fundamental concepts of phase stability, interfaces and defects play a key role in understanding these crucial issues. These concepts are reviewed in a crucial fashion.