The advent of integrated circuit (IC) technology has triggered an era of electronics with previously unimaginable capabilities and computing power. Decades of progress were driven by the continued miniaturization of transistor dimensions to yield greater circuit density and functionality at lower cost per function. Although transistor scaling has provided for enhanced performance, it has also resulted in increased in power per unit area of a chip. In order to improve the energy-efficiency of electronic circuits, small swing switches are interesting candidates to replace or complement the MOSFETs used today. In this book, by employing two- and three-dimensional numerical simulations the electrical characteristics and short channel behavior of various small swing multi-gate transistors based on advanced SOI technology have been investigated. These include single-gate, double-gate, gate-all-around nanowire FETs with different channel materials including Carbon Nanotube (CNT), Silicon Nanowire (NW) and III-V compound semiconductors which are promising candidates for future of nanoscale CMOS technologies.