Inversion-Layer Quantization and Hot-Carrier Effects in Ultrathin-Gate MOSFETs: Impact on Channel Thermal Noise

Below approximately 2 nm equivalent oxide thickness, gate tunnelling and inversion-layer quantization modify carrier statistics and energy dissipation in metal-oxide-semiconductor field-effect transistor (MOSFET) channels, yet their effect on microscopic thermal fluctuations remains unresolved. By treating the channel as an open quantum-transport system, tunnelling-induced energy loss is embedded into the electron energy-balance equation to obtain quantum-corrected hot-electron temperature and mobility degradation. Inversion-layer quantization is further accounted for through surface-potential elevation and threshold-voltage shift, yielding a self-consistent drain-current description and a corresponding channel thermal noise framework. Monte Carlo simulations provide trend comparisons. The results show that omitting quantum effects overestimates the thermal noise, the correction being governed almost entirely by inversion-layer quantization while the tunnelling contribution is negligible. The hot-carrier effect, strengthened by high fields and short channels, enhances the thermal noise and outweighs this quantization-induced suppression, leading to a net increase relative to the thermal-equilibrium baseline.