Hafnium is a chemical element with the symbol Hf and atomic number 72. This book brings together contributions from experts in their related fields to illustrate the significance and importance of hafnium in different forms. This book is composed of six chapters written by experts in their respective fields making this book valuable to the group-IV materials science communities. The subjects presented in the book offer a general overview of the important issues of various hafnium compounds, e.g. Hafnium nitride/Hafnium carbide application as a coating material, and Hafnium oxide application as the dielectric layer in non-volatile memory/state-of-the-art CMOS devices. We believe the book is of great scientific and educational value for many readers. Readers thus can familiarize themselves with the latest knowledge in the related fields.