Book excerpt: This book provides a unique review of various aspects of metallic contamination in Si and Ge-based semiconductors. It discusses all of the important metals including their origin during crystal and/or device manufacturing, their fundamental properties, their characterization techniques and their impact on electrical devices’ performance. Several control and possible gettering approaches are addressed. The book offers a valuable reference guide for all researchers and engineers studying advanced and state-of-the-art micro- and nano-electronic semiconductor devices and circuits. Adopting an interdisciplinary approach, it combines perspectives from e.g. material science, defect engineering, device processing, defect and device characterization, and device physics and engineering.