The scaling of semiconductor process technologies has been continuing for more than four decades. Advancements in process technologies are the fuel that has been moving the semiconductor industry. In response to growing customer demand for applications that require integrated circuits with enhanced performance and functionality at reduced cost, a new process generation has been introduced by the semiconductor industry every two to three years during the past forty years. The challenge for enhancing the performance and functionality of integrated circuits has traditionally been managing the greater design and manufacturing complexity and higher power consumption. As stressed throughout this book, the generation, distribution, and dissipation of power are at the forefront of current problems faced by integrated circuit designers.