Nanotechnology deals with the creation and utilization of materials, devices and systems on the nanometer-length scale. Higher speed can be achieved with a smaller device size. This rapid rate of feature size downscaling would lead to a significant short channel effects limitations. DMG MOSFET has been proposed as potential candidate to combat SCEs. Moreover, the design of both digital and analog systems in which the devices are operated in the subthreshold regime has evinced a lot of interest due to the tremendous market demand for extremely low power applications It is highly important to understand the device physics and development of corresponding accurate device model of subthreshold performances for application of MOSFET in the integrated circuit simulation and design in parallel to the process technology advancement. At present, there is a general consensus that the surface potential based modeling approach preserves device physics to describe the device operation with high accuracy. This book is designed to serve as a reference book for subthreshold surface-potential based short channel MOSFET device modeling using TCAD tools.