I. Introduction
Technology and market trends lead to smaller electronic devices and result in demand for many functions in one product. These products require higher system clock frequencies and integrate more transistors into one die. The International Technology Roadmap for Semiconductors (ITRS) roadmap [1] predicts that, by the year 2010, an 18-nm CMOS process will be made available and the operating frequency will be near 15 GHz in an EMC-confirmed system. Compared to the technologies of year 2006, the total chip size will be roughly the same while the functions per chip, the transistor density, and the on-chip clock speed will all be doubled, and the gate length will shrink by two-thirds.