Parameters that determine the performance of silicon-based Field Effect Transistors (FET) devices in the presence of degenerate doping, often are not modeled properly and so require precise analysis to improve modeling accuracy. The book is focused on the extraction of parameters for silicon-based FET models that critically determine the FET performance at room temperature as well as at very low temperatures. Emphasize is put on analysis that is based on the device physics, especially at low (cryogenic) temperatures. Performance of gate-all-around (GAA) nanowire FETs, and stacked nanosheet complementary FETs (C-FET) are also discussed.