Abstract <p>This work investigates the cryogenic performance of 5 nm FinFET and Gate-All-Around (GAA) transistors, focusing on their electrical, thermal, and noise properties. Both devices exhibit better transconductance (<i>g</i>_m), threshold voltage (<i>V</i>_th), drain current (<i>I</i>_DS), subthreshold swing (SS), leakage current, on/off ratio, and noise figure (<i>F</i>) at low temperatures. FinFETs show maximum transconductance of&#xa0; 79.3 µS, an SS of about 20 mV/dec, and an on/off current ratio of about 10³⁵ at low temperature. They can drive currents of up to 341 µA at 20 K. GAA transistors, on the other hand, have better electrostatic control, with a higher <i>V</i>_th (0.73 V vs. 0.65 V for FinFET), a sharper SS of around 10 mV/dec, and a better on/off current ratio of about 10⁴⁹. Thermal study indicates that FinFETs exhibit higher self-heating (~91 K) than GAA (~80.5&#xa0;K), with heat concentrated near the drain end of the channel in FinFETs and near the source end of the channel in GAA transistors. Noise study shows that both thermal and generation–recombination noises are lower at cryogenic temperatures. Multi-gate wrapping can further reduce these noises. Overall, at cryogenic temperatures, the 5 nm FinFET architecture is more suitable for high-current electronics, whereas GAA transistors are more favourable for low-noise and low-power electronics, demonstrating their potential applications in quantum computers and other cryogenic technologies.</p>