This book systematically examines the results of an investigation of electronic and molecular processes on the surface of semiconductors, taking place at their interaction with particles of a gas environment or in the course of superficial alloying by atoms of metals. The main subject of the book is the analysis of interaction of semiconductors with foreign atoms and molecules from a gas environment and from beams of elements, bombarding a surface. This book consists of five chapters, including 13 tables, 122 figures and bibliography based on over 500 sources, including author's publications and data originally never published in English before. The book acquaints the reader with basic concepts and positions, used at the description of interaction of semiconductor surface with foreign atoms and molecules. Demonstration of opportunities arising from the usage of local and collective approaches to the analysis of electronic and molecular processes on a surface is useful though insufficient in determining the sensitivity for adsorption of a semiconductors' surface.