A method for forming a ring pattern is disclosed. The ring pattern has a first wall and a second wall. The method includes the following steps: (a) providing a substrate; (b) forming a dielectric layer on the substrate; (c) forming a first patterned photoresist layer on the dielectric layer, the first patterned photoresist layer defining the first wall; (d) etching the dielectric layer to a predetermined depth by using the first patterned photoresist as a mask, and then removing the first patterned photoresist layer; (e) forming a second patterned photoresist layer on the dielectric layer, the second patterned photoresist layer defining the second wall; (f) etching the dielectric layer by using the second patterned photoresist layer as a mask so as to form the ring pattern having the first wall and the second wall.