Low voltage operating organic devices and circuits have been realized using atomic layer deposition deposited aluminum oxide thin film as dielectric layer. The dielectric film has per unit area capacitance of 165 nF/cm2 and leakage current of 1 nA/cm2 at 1 MV/cm. The devices and circuits use the small-molecule hydrocarbon pentacene as the active semiconductor material. Transistors,inverters,and ring oscillators with operating voltage lower than 5 V were obtained. The mobility of organic field-effect transistors was extracted to be 0.16 cm2/Vs in saturation range,the threshold voltage is 0.3 V,and the on/off current ratio is larger than 105. The gain of inverters is estimated to be 12 at -5 V supply voltage,and the propagation delay is 0.25 ms per stage in 5-stage ring oscillators. Low voltage operating organic devices and circuits have been used using atomic layer deposition deposited aluminum oxide thin film as dielectric layer. The dielectric film has per unit area capacitance of 165 nF / cm2 and leakage current of 1 nA / cm2 at 1 MV / cm. The devices and circuits use the small-molecule hydrocarbon pentacene as the active semiconductor material. Transistors, inverters, and ring oscillators with operating voltages lower than 5 V were obtained. The mobility of organic field-effect transistors was extracted to be 0.16 cm2 / Vs in saturation range, the threshold voltage is 0.3 V, and the on / off current ratio is larger than 105. The gain of inverters is estimated to be 12 at -5 V supply voltage, and the propagation delay is 0.25 ms per stage in 5 -stage ring oscillators.