A theoretical breakdown model based on anode hole injection is presented for evaluating the time dependence of injected electron and generated substrate hole current under constant voltage stress for thin gate oxide MOS devices. The model considers the effect of poly-depletion, quantum yield, first order trapping kinetics and different tunneling conditions for determining the time variation of hole current during constant voltage stress and correlates it to the buildup of the positive charge inside the oxide during the time dependent oxide breakdown process. The model is shown to agree well with the experimental results. Moreover, using the proposed model the intrinsic charge to breakdown Q(BD) and the time to breakdown t(BD) of thin gate oxide MOS devices can be satisfactorily predicted at different oxide voltages.