As a promising alternative to the fundamental device structure, the gate-all-around silicon nanowire transistor (GAA SNWT) has been studied extensively for decades. In this chapter, the device physics, compact modeling, and fabrication process of GAA SNWT are systematically reviewed, as well as its potential applications in terms of different technology diversities. In the first part, the bulk-Si based integration scheme, quasi-ballistic transport characterization, parasitic capacitance, and self-heating modeling of GAA SNWT are presented. Following that, the variability and reliability physics and models of GAA SNWT are studied in-depth. Finally, the application examples in electrostatic discharging, radio frequency/analog circuit, and bio-sensor of GAA SNWT are demonstrated.