In one embodiment, a semiconductor device comprises a base and a tapered wall formed on the base. The wall has a midline and also has an inner sidewall and an outer sidewall. The inner sidewall and the outer sidewall are substantially symmetrical with each other in relation to the midline. Thus, the reliability of the semiconductor capacitor structure can be improved and the throughput can be increased. Also, further scaling down of semiconductor devices can be facilitated with the principles of the present invention.