A study of the performance and hot-electron reliability of submicron n-channel MOSFET's is presented. Well-established hot-electron-based physical models are adequate in explaining the general behaviors of the drain, substrate, and gate currents of these devices. These results suggest that the basic physics is rather well-understood and the design criteria developed for micron-size devices can be extended to cover their deep-submicron counterparts. Hot-electron studies reveal a channel-length dependence in device degradation. This phenomenon together with gate-induced drain leakage current [1] will impose an upper limit on the supply voltage and a lower limit on the gate oxide thickness. Based on device degradation results alone, the power supply voltage for a quarter-micron device with oxide thickness of 86 Å should be limited to 2.5 V if no degradation-resistant structure is used.