The temperature effects of both gate-all-around polycrystalline silicon nanowire (GAA poly-Si NW) junctionless (JL) and inversion mode (IM) transistor devices at various temperatures (77-410 K) were investigated. The electrical characteristics of these devices, such as subthreshold swing (SS), threshold voltage (Vth), and drain-induced barrier lowering (DIBL), were also characterized and compared in this study. Moreover, JL devices with different doping concentrations at various temperatures were also discussed. Both Vth and Ion showed significant doping concentration dependences for JL devices with doping concentrations of 1 × 1019 and 5 × 1019cm%3. However, the electrical characteristics of JL devices showed less thermal sensitivity when the doping concentration reached 1020cm%3.