The main purpose of this book is to present some results in the field of generation and annealing of radiation defects in MOS structures received by the authors in their joined work during the last years. Most of the present results are a product of the collaboration between Bulgarian Academy of Sciences, Joint Institute of Nuclear Research and Russian Academy of Sciences. Metal-oxide-semiconductor (MOS) structure is (and it will be in the next several decades) the basis of electronic and microelectronic devices. Some MOS devices are faced with the necessity of working in radiation ambient and it is very important to improve their radiation hardness. On the other hand, ion implantation is a stage of some MOS devices production and along with its advantages it generates radiation defects. Radiation defects produced by ion implantation or another high energy irradiation (in particular, gamma or MeV electrons) are reviewed in the book. Special attention is paid to the characteristics of dually treated MOS structures. Investigations into effects of secondary irradiation of pre-implanted MOS structures are carried out.