This book presents the fundamentals of novel gate dielectrics that are being introduced into semiconductor manufacturing to ensure the continuous scaling of CMOS devices. As this is a rapidly evolving field of research we choose to focus on the materials that determine the performance of device applications. Most of these materials are transition metal oxides. Ironically, the d-orbitals responsible for the high dielectric constant cause severe integration difficulties, thus intrinsically limiting high-k dielectrics. Though new in the electronics industry many of these materials are well-known in the field of ceramics, and we describe this unique connection. The complexity of the structure-property relations in TM oxides requires the use of state-of-the-art first-principles calculations. Several chapters give a detailed description of the modern theory of polarization, and heterojunction band discontinuity within the framework of the density functional theory. Experimental methods include oxide melt solution calorimetry and differential scanning calorimetry, Raman scattering and other optical characterization techniques, transmission electron microscopy, and X-ray photoelectron spectroscopy. Many of the problems encountered in the world of CMOS are also relevant for other semiconductors such as GaAs. A comprehensive review of recent developments in this field is thus also given.