Method for forming a high-density dram cell with a rugged polysilicon

Abstract

In the preferred embodiment for forming a rugged polysilicon cup-shaped capacitor of a dynamic random access memory cell, a first dielectric layer is formed on a semiconductor substrate. A second dielectric layer is formed on the first dielectric layer, followed by the formation of a first conductive layer on the second dielectric layer. Portions of the first conductive layer and the second dielectric layer are then removed to define an opening therein. A second conductive layer is formed conformably on the substrate within the opening and on the first conductive layer. A sidewall structure is then formed within the opening on sidewalls of the second conductive layer. Next, a removing step is performed to remove a portion of the second conductive layer which is uncovered by the sidewall structure. The sidewall structure and a portion of the first dielectric layer are removed, using the residual second conductive layer as a mask, to define a contact hole within the first dielectric layer. A third conductive layer is formed conformably on the substrate and formed to fill up the contact hole. Portions of the first conductive layer and the third conductive layer are removed to define a storage node. The second dielectric layer is then removed and a third dielectric layer is formed on the substrate. Finally, a fourth conductive layer is formed on the third dielectric layer to complete the formation of the capacitor.