The hot‐carrier immunity of submicrometer (0.8 &mgr;m)n‐channel metal‐oxide‐semiconductor field‐effect transistors with thin (∼8.6 nm) oxynitride gate dielectrics prepared by rapid thermal reoxidation (RTO) of rapidly thermal nitrided (RTN) SiO2has been studied. The hot‐carrier immunity was evaluated in terms of hot‐carrier‐induced transconductance degradation (&Dgr;Gm/Gm0) and interface state generation (&Dgr;Dit/Dit0) which was measured by using charge pumping current (Icp) measurement. It is found that for improved device performance and reliability, there exists an optimum RTO condition for a given RTN SiO2. In addition, a strong correlation between &Dgr;Dit/Dit0and &Dgr;Gm/Gm0has been observed.