This book covers a wide range of topics on work function and band alignment, from the basics to practical examples. Work function and band alignment determine electric properties at the interface including surfaces, such as electron emission, the Schottky barrier height, and ohmic contact. Basic physics is used to systematically explain how to adjust and measure work function and how to modify the band alignment required for controlling work function in functional materials and electrodes. Methods introduced in the book help to improve device performance and to solve the problems of controlling the voltage and efficiency of devices in a great variety of applications, including electronic devices, optical devices such as displays, and energy devices such as solar cells and batteries. Understanding the technical methods necessary for controlling work function and band alignment can help to solve problems such as non-ohmic contact at source-electrode or drain-electrode interfaces in metal-oxide-silicon structures, which directly contributes to improving power saving and reducing heat generation in computers.