A self-consistent qualitative model for the degradation and mechanism of high-frequency AC hot-carrier effects has been successfully developed and experimentally verified. According to the model, hot electrons are injected to break the Si-H bounds and produce the trivalent silicon. Subsequently, hole trapping and electron trapping with the trivalent silicon occur and the released energy produces interface states in the channel region. This leads to the degradation in DDD and LDD MOSFETs. But hot-electron-induced charge trapping also occurs in the n- region of LDD MOSFETs, which causes Gm degradation. Applying the developed model, degradation behaviors and mechanism in AC stress can be well explained. Moreover, worst-case inverter-like stress in DDD MOSFETs is shown to have a greater degradation than the DC stress. Maximum degradation in MOSFETs has been observed at certain frequencies.