A new model for the post-breakdown conductance of ultrathin gate oxides based on the generalized diode equation is presented. The model is expressed in terms of the Lambert W function, that is, the inverse of the function w → wew. We show that this alternative formulation improves a previous one, the quantum point contact model, especially in the low bias range, where the role played by the semiconductor electrodes cannot be overlooked. The practical implementation of the proposed equations is discussed. © 2005 IEEE.