This book examines the potential application of semiconductor materials for gas sensor production on the basis of their fundamental, theoretical, and experimental studies. Some of these materials or their composites were applied for semiconductor gas sensor production for the first time. Special attention is paid to the model materials A2B6, which are used in the form of films with biographic surface as well as with the surface doped by donor (In, Cd, Sn, Pt, Pd etc.) and acceptor (Se and others) particles. Results of application of metal-oxide materials as adsorptionally sensitive elements are also represented in this book. These elements were produced and tested in the form of simple oxides (as SnO2, In2O3, for example) as well as in the form of composite oxide metal complexes (SnWO4, ZnO:In2O3 etc.). The book examines in detail the influence of doping on different materials and their adsorption sensitivity, persistence, selectivity, dynamic and kinetic characteristics, and other parameters. Results of thorough studies of degradation of semiconductor sensor material characteristics, when in working gas atmospheres, are represented in a special section of the book. Adsorptionally sensitive parameters of amorphous silicon, micro-, macro- and nanoporous silicon are examined and results of Si structure testing as gas sensors are also discussed in this book.