The charge-to-breakdown (Q(bd)) for p(+)-poly-Si MOS capacitors under positive and negative gate-bias stress was investigated. Among the various boron-implanted poly-Si samples, Q(bd)(+) increases with dopant concentration, but Q(bd)(-) decreases with the boron concentration. Meanwhile a large difference was found between the Q(bd)(+) and Q(bd)(-) values. Evidence for various degree of band bending of poly-Si was observed from C-V and Fowler-Nordheim tunneling measurements. From gate-voltage shift (Delta V-g) data after constant current stress, the centroid of the generated positive trapped charge can be determined. We modified the charge-trapping model to explain the above Q(bd) behavior. Hole trapping is the cause of oxide breakdown. The observed difference between gate-positive and gate-negative Q(bd) is due to a polarity-dependent critical trapped charge density which depends on the critical electrical field somehow related to the boron implantation. As the generated positive trapped charge reaches a critical value, part of the localized electric field near the anode disappears and the remaining part of the electric field (E) is enhanced. This critical E field triggers thermal runaway and oxide breakdown. Therefore, we determine that the amount of Q(bd) is related to the boron implantation.