In the high-k/SiO2 stacked dielectric MOS capacitor, it is believed that the electrons captured by the defects associated with the oxygen vacancies formed in high-k dielectric preparation may affect the trap-assisted tunneling current of the device. In this work, high bandgap material was utilized as substrate for its considerable interface states which are important to enhance the effect of trapped charges on the tunneling current. It was found that the electrons captured in high-k/SiO2 interface layer were crucial to block the current conduction path. Two-state current behavior was clearly observed and investigated by this mechanism. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.042112jes] All rights reserved.