By electrochemical deposition, an anodic oxide film composed of a compound containing HgTeO3, ZnTeO3, and TeO2-rich components was formed on a Hg1-xZnxTe material surface. After the anodic oxide film deposition, a voltage annealing process in which the electrical potential is maintained constant was applied. This process improves the quality of the anodic oxide film. The capacitance-voltage (C-V) measurement of the metal-insulator-semiconductor (MIS) capacitor of Ni/In/ZnS/oxide/Hg1-xZnxTe confirms the enhancement of the stability of MIS capacitor characteristics by the voltage annealing process.