Indium tin oxide (ITO) thin films were deposited by magnetron sputtering from a ceramic target, and annealed at temperatures up to 1000 °C in N 2 atmosphere. Some samples were capped in a-Si:H or spin-on glass to prevent residual oxygen contamination from the annealing ambient, and annihilation of oxygen vacancies. The electrical and optical properties were measured before and after annealing. It is found that the protecting layer effectively limits the ITO degradation up to 900 °C, whereas high transparency is preserved in all cases. The results indicate the applicability of the procedure to high temperature devices, and opens the way to the application of a variety of nanostructured materials in advanced photovoltaic devices.