The invention provides a novel technology where a TFT array substrate for a display device is formed with three photomasks. The invention is achieved by using the novel technology in combination with a well-known four-masks process. For the novel technology, during the lithography process where a photosensitive acrylic resin film is used to make contacts, taper patterns required for general through holes are formed simultaneously with a fine pattern formed in a light shielding area that is tapered more approximately to vertical, using a photomask with phase-shift effect. Thus the pixel electrode pattern can be separated without using lithography process in subsequent processes.