The electronic device based on Metal Oxide Semiconductor (MOS) structure is the most important component of a large-scale integrated circuit, and is therefore a fundamental building block of the information society. Indeed, high quality MOS structure is the key to achieving high performance devices and integrated circuits. Meanwhile, the control of interface physics, process and characterization methods determine the quality of MOS structure. This book tries to answer five key questions: Why are high-performance integrated circuits bonded together so closely with MOS structure? Which physical phenomena occur in MOS structure? How do these phenomena affect the performance of MOS structure? How can we observe and quantify these phenomena scientifically? How to control the above phenomena through process? Principles are explained based on common experimental phenomena, from sensibility to rationality, via abundant experimental examples focusing on MOS structure, including specific experimental steps with a strong level of operability. This book will be an essential reference for engineers in semiconductor related fields and academics and postgraduates within the field of microelectronics.