| 摘要 |
The method of the present invention for forming a capacitor on a semiconductor substrate includes the following steps. At first, a first oxide layer is formed over the substrate and a nitride layer is then formed over the oxide layer. A second oxide layer is formed over the nitride layer and a first silicon layer is formed over the second oxide layer. Next, a node opening is defined in the first silicon layer, the second oxide layer, and the nitride layer, upon the first oxide layer. Sidewall structures are then formed on sidewalls of the node opening. A contact opening is then defined in the first oxide layer under the node opening. The contact opening is defined in the first oxide layer under a region uncovered by the sidewall structures. The sidewall structures and a portion of the nitride layer nearby the node opening are removed to form undercut structures under the second oxide layer. A second silicon layer is then formed conformably over the contact opening, the undercut structures, the node opening, and the first silicon layer. A filling layer is formed over the second silicon layer. A planarizing is performed to planarize the substrate down to a surface of the second oxide layer. The filling layer and the second oxide layer are then removed. The nitride layer is also removed. A dielectric film is then formed conformably over the second silicon layer. Finally, a conductive layer is formed over the dielectric layer.
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