The inversion current conduction mechanism for MOS(p) capacitors with ultrathin oxides was analyzed from another aspect of bulk traps in this paper. The relationships between deep depletion and generation-recombination current were also studied. It was found that the generation-recombination current due to bulk traps is proportional to the deep-depletion width and dominates the inversion tunneling current. Moreover, it was observed that the inversion tunneling current levels for SiO2, Al2O3, and HfO2 gate dielectrics were different. This discrepancy was explained with their energy band diagrams. Due to the small conduction-band offset of HfO2, the gate dielectrics of HfO2 show a worse capability to block the inversion tunneling current in the saturation region than Al2O3 gate dielectrics.