An array substrate for use in an X-ray sensing device is fabricated using an etching stopper that enables good control of the etching process and that prevents over-etch of drain electrodes and second capacitor electrodes while forming contact holes and a cutting furrow. The etching stopper is located in a tiling portion that is utilized for tiling substrates to form a large-sized X-ray detector. During fabrication, gate lines can have gate-protruded portions located near the etching stopper, and the etching stopper can have stopper-protruded portions near the gate lines. The stopper-protruded portions electrically connect to the gate-protruded portions through gate line contact holes such that the etching stopper and the gate lines have equipotentials. This can reduce static electricity damage.