The interaction of semiconductor surfaces with deposited metals is very important for understanding many aspects of the behavior of microelectronic devices. The early stages of metal-semiconductor interface formation are amenable to analysis with surface sensitive techniques. The most important characteristic of metal semiconductor interface is nature of the potential barrier between the Fermi level in the metal and the majority carrier band edge of semiconductor of that interface. The study of metal / semiconductor (Si) reactions are of great importance present in every semiconductor device.The present book is an outcome of investigations of structural, morphological, magnetic and electrical behaviour of metal (Co, Cr, Ni) / semiconductor (Si) system.