The impact of a soft breakdown-induced leaky weak spot occurring in the channel has been analyzed by two dimensional simulations of a metal oxide semiconductor field effect transistor within the charge sheet approximation. The model proves very efficient in reproducing the device characteristics variations after soft breakdown (SBD) and enables to properly interpret the correlation observed between device parameter shift (e.g., threshold voltage) and stress-induced gate leakage current. A partitioning study allows us to extract an expression for the channel debiasing at V-d>0 and to discriminate each impact of SBD on device characteristics. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3065414]