A memory device having improved sensing speed and reliability and a method of forming the same are provided. The memory device includes a first dielectric layer having a low k value over a semiconductor substrate, a second dielectric layer having a second k value over the first dielectric layer, and a capacitor formed in the second dielectric layer wherein the capacitor comprises a cup region at least partially filled by the third dielectric layer. The memory device further includes a third dielectric layer over the second dielectric layer and a bitline over the third dielectric layer. The bitline is electrically coupled to the capacitor. A void having great dimensions is preferably formed in the cup region of the capacitor.