A thin film transistor liquid array substrate includes forming a plurality of amorphous silicon thin film transistors and storage capacities on a transparent substrate, wherein the amorphous silicon thin film transistors and the storage capacities are arranged in an array pattern. The storage capacitor has a top electrode and a bottom electrode, which are made of transparent conductive material to increase aperture ratio. A method of making the amorphous silicon thin film transistors and the storage capacities includes four photomask processes and a back exposure technique. Because the present invention only uses four photomask processes, the number of photomasks used in the process of the present invention is less than the conventional method, and the cost of fabrication is lower also.