The model and the intrinsic carrier concentration of hexagonal ZnO single-crystal microtubes are investigated by capacitance-voltage (C-V) measurements. The film fabricated by hydrothermal method on p-type silicon (I I I) is composed of microtubes with hexagonal tubular structure, which have diameters of 3-4 mu m and lengths in the range of 10-20 mu m. In this article, the structure of ZnO/Si was analyzed and modeled, and the total capacitance model of the sample was deduced by analyzing the C-V characteristics of the ZnO. The small-signal equivalent scheme of the sample capacitance is also obtained. The C-V profiling calculated by the model agreed with the measured C-V curve. As a simple application of the model, the intrinsic carrier-concentration distribution of ZnO was extracted. (c) 2006 American Vacuum Society.