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.

Abstract: The present invention provides a method of forming trench capacitor with a sacrificial silicon nitride. A deep trench structure is formed in a substrate. A TEOS oxide layer is formed on the substrate and filled in said trench region, etched to a first level subsequently, wherein a portion of the TEOS oxide layer is remained in the trench region and a portion of the substrate exposed to form a trench sidewall. A thermally oxidation process is performed to form a collar oxide on the exposed substrate. A silicon nitride sidewall is formed on the collar oxide, then removing the residual TEOS oxide layer by wet etching. A bottom cell plate is formed in the lower trench region. The silicon nitride sidewall is removed. A dielectric film is formed along a surface of the bottom cell plate, the collar oxide, and the substrate, subsequently, a first conductive layer is formed on said dielectric film and refill in the trench region.