Negative bias temperature instabilities (NBTI) in SiOx(N)/HfSiO(N)/TaN based pMOSFETs are investigated. It is shown that nitrogen-incorporation in the gate stack (either by NH3 anneals or decoupled plasma nitridation, DPN) result in much enhanced NBTI-Device degradation is mainly due to fast (interface) state generation in the non-nitrided stacks, while a substantial contribution of the defects produced in the nitrided stacks are slow (bulk) states. The kinetics of fast interface states is modeled within a reaction-dispersive transport model, taking into account the dispersive transport of protons generated from the depassivation of trivalent Si dangling bonds at the Si/SiOx interace (P-b0 centers). The generation of slow states in the nitrided stacks is simulated by an electrochemical model, considering the electric field and hole assisted breaking of nitrogen-related defects, tentatively attributed to Si2N center dot or Hf2N center dot dangling bonds. A correlation between NBTI and recovery is also found, namely that enhanced NBTl in nitrided stacks results in enhanced recovery. This suggests that recovery mainly arises from the detrapping of holes at the N-related defects. (c) 2006 Elsevier Ltd. All rights reserved.