Pentacene thin film transistors were fabricated and characterized with PVA thin films as a gate dielectric. The maximum process temperature was 70 degrees C, which corresponds to a baking temperature of the spin-coated polymeric dielectric. Glass and flexible PET foils were used as substrates. Theses devices showed high performance electrical characteristics and worked at a low operating voltage of -5V. The highest field effect mobility of 2.6cm(2)/Vs and the lowest threshold voltage of -1.7V were obtained on a flexible substrate.