The anodization of Ti to obtain high-quality, ultra-thin gate insulators for organic field-effect transistors (OFET), was analyzed. An anodized-TiO 2 surface was capped with an ultrathin layer of poly(α-methylstyrene) (PAMS) spun from dilute solution. It was observed that the anodization voltage of 5 V corresponded to an ultra-thin layer of the oxide with a thickness in the region of 7-8 nm. The gate leakage was revealed by an apparent positive drain current at zero drain voltage, but non-zero gate voltage. The results show that the PAMS-capped TiO2 device displays tenfold lower leakage than an uncapped TiO2 OFET with similar semiconductor/insulator overlap.