In this paper a comprehensive study of the worst case hot carrier stress conditions for p-channel partially depleted SOI MOSFETs is carried out. It is found that while stress at maximum gate current results to the conventional PMOSFET degradation mechanism (i.e., electron trapping in the gate oxide on the drain side), significant damage is also introduced following stress at the high gate/high drain voltage (V-G = V-D) condition. A series of experiments unambiguously demonstrate that this damage is not caused by hot hole injection and that device degradation mechanism at V-G = V-D stress condition (formation of interface states and positive oxide charges) is in fact due to negative bias temperature instability which is activated because of the self-heating effect. In addition, stress at high temperature is found to result in a shift of the worst case stress condition from maximum gate current to V-G = V-D. (c) 2006 Elsevier Ltd. All rights reserved.