A method for fabricating a cylindrical capacitor is provided. This invention uses a composite structure composed of stacked barrier/scarificing/mask layers to prevent the contact plug of the capacitor from being attacked by wet etchants. An insulating layer is formed over a substrate having a source region, a drain region, and a gate electrode. Then a barrier layer, a sacrificing layer and a mask layer are sequentially formed over the insulating layer. Next, a contact hole is formed over the source region and spacers are formed on the sidewalls of the contact hole. After a storage electrode of the capacitor is formed and exposed portions of the mask layer are removed, the sacrificing layer is isotropically etched using the spacers and the barrier layer as stopping layers. Thereafter, a capacitor dielectric layer and an opposite electrode are formed over the storage electrode thereby completing the capacitor.