Book excerpt: This book describes the physical operation of the Tunnel Field-effect Transistor (TFET) and circuits built with this device. Whereas the majority of publications on TFETs describe in detail the device, its characteristics, variants and performance, this will be the first book addressing TFET integrated circuits (TFET ICs). The authors describe the peculiarities of TFET ICs and their differences with MOSFETs. They also develop and analyze a number of logic circuits and memories. The discussion also includes complex circuits combining CMOS and TFET, as well as a potential fabrication process in Silicon.