Method for forming a deep trench capacitor of a dram cell

Abstract

A method of forming a trench capacitor over a semiconductor substrate comprises the following steps. First, a nitride layer is formed on the substrate. Then, a first oxide layer is formed on the nitride layer. Next, the first oxide layer and the nitride layer are etched to expose a portion of the surface of the substrate. An etching back step is performed to etch the nitride layer to pull back the sidewalls of the nitride layer. Next, the second oxide layer is formed above the first oxide layer, the nitride layer and the substrate. An etching step is done to form the trench structure on the substrate by using the first oxide layer as a mask. Then, a wet etching step is performed to remove the first oxide layer and the second oxide layer. Next, a doping step is done to form the doped region in the trench structure. A dielectric layer is then formed above the doped region. A conducting layer is formed on the dielectric layer, wherein the conducting layer is coupled with a drain.