Self-organized nanotube arrays of TiO₂ have been grown from titanium (Ti) thin films deposited on p-type Si(100) substrates. Structural and morphological characterizations carried out by X-ray diffraction and scanning electron microcopy indicate that the sputtered crystalline Ti thin films used for subsequent anodization are hexagonally closed packed (hcp-Ti) and show a columnar morphology. Electrochemical anodization of the Ti films was carried out by potentiostatic experiments in 1M H₃PO₄+1M NaOH+0.5wt% HF electrolyte at room temperature. The TiO₂ nanotubes on a semiconductor substrate have an average tube length of approximately 560nm, diameter in the order of 80nm and wall thickness approximately 20nm.