A method of fabricating an active device array substrate is provided. A substrate having scan lines, data lines and active devices formed thereon is provided. Each of the active devices is electrically connected to the corresponding scan line and data line. An organic material layer is formed over the substrate to cover the scan lines, the data lines and the active devices. Then, a plasma treatment is performed to the surface of the organic material layer to form a number of concave patterns. The dimension of each of the concave patterns is smaller than one micrometer. Afterward, pixel electrodes are formed on the organic material layer and each of the pixel electrodes is electrically connected to one of the corresponding active devices.