Uncertainty in key parameters within a chip and between different chips in the deep sub micron area plays a more and more important role. As a result manufacturing process spreads need to be considered during the design process. Quantitative methodology is needed to ensure faultless functionality despite existing process variations within given bounds during product development. This book presents the technological physical and mathematical fundamentals for a design paradigm shift from a deterministic process to a probability-orientated design process for microelectronic circuits. Readers will learn to evaluate the different sources of variations in the design flow in order to establish different design variants while applying appropriate methods and tools to evaluate and optimize their design.