Alumina (Al2O3) thin films derived from a sol-gel wet chemistry process were used to prepare capacitors with a simple MIM structure of Al/Al2O3/Pt. Driven by the external applied electric field, the phenomenon of anodic oxidation has been observed and confirmed at the Al/Al(2)O(3)( )interface, resulting in the formation of a new alumina blocking layer (BL). Importantly, similar to the product of anodic oxidation of aluminum in liquid electrolytes, the blocking layer here exhibited excellent electrical characteristic and voltage-dependent growth mode as well, which endowed the capacitor with less defective electrode/film structure and self-enhanced electrical performance under the application of external voltage. Specifically, an similar to 50% enhancement of the maximum working voltage and better capacitance characteristics of the thin film capacitor can be achieved. With the impedance and finite element analyses, the electrical characteristic of the BL and its corresponding effect on the alumina capacitor were explored in depth. (C) 2019 Elsevier Ltd. All rights reserved.