Book excerpt: This book examines the critical differences between current and next-generation Si technologies (CMOS, BiCMOS and SiC) and technology platforms (e.g. system-on-chip) in mm-wave wireless applications. We provide a basic overview of the two technologies from a technical standpoint, followed by a review of the state-of-the-art of several key building blocks in wireless systems. The influences of system requirements on the choice of semiconductor technology are vital to understanding the merits of CMOS and BiCMOS devices – e.g., output power, battery life, adjacent channel interference, cost restrictions, and so forth. These requirements, in turn, affect component-level design and performance metrics of oscillators, mixers, power and low-noise amplifiers, as well as phase-locked loops and data converters. Finally, the book offers a peek into the next generation of wireless technologies such as THz -band systems and future 6G applications.