Metal-Insulator-Semiconductor (MIS) Schottky diodes were fabricated to study Fermi level unpinning by use of a thin TiOx insulator. For Ti-TiOx-n-Si junctions, the Schottky barrier height (SBH) was pinned due to O diffusion from TiOx into Ti during thermal anneals, as observed from XPS depth profiles. A thin AlOx barrier inserted between the Ti and the TiOx prevented O diffusion from TiOx into Ti, allowing SBH unpinning to be maintained after 450 °C anneals.