A method of forming a ring-type capacitor is provided. The method includes providing a substrate; forming a patterned mask layer on the substrate, the patterned mask layer defining a ring pattern; removing the substrate by using the patterned mask layer as a mask to form a ring-type trench in the substrate; the ring-type trench including an inner wall and an outer wall; and forming a capacitor structure on the inner wall and the outer wall of the ring-type trench.