The present application discloses a semiconductor device structure and a method for forming the same. The method includes forming a pillar over a substrate, forming a first ring structure over a sidewall of the pillar, removing the pillar to form a first opening surrounded by the first ring structure, forming a second ring structure in the first opening, forming a third ring structure surrounding the first ring structure after the first opening is formed, and removing the first ring structure to form a gap between the second and third ring structures. A semiconductor device structure includes a dielectric layer over a substrate, a first ring structure over the dielectric layer, and a second ring structure over the dielectric layer and surrounding the first ring structure, wherein the first and the second ring structures have a first common center.