Metal-insulator-metal (MIM) diodes with bulk-limited current conduction asymmetry employing interposed Al 2 O 3 layer in 6-nm-thick HfO 2 film have been investigated. The current density is decreased as the Al 2 O 3 layer is located far from the electron injection electrode (i.e., cathode). Also, the work function difference of the electrode does not affect the asymmetry of the MIM diodes. Asymmetry of current conduction is attributed to the control of bulk-limited current conduction by the interposed Al 2 O 3 layer. Physicochemical analysis also confirms the dependence of the location of Al 2 O 3 layer on the bulk-limited current asymmetry.