Patent ID: 6960503

Claim:
A method for fabricating a trench capacitor, comprising: providing a substrate having a deep trench etched therein; doping the deep trench to form a buried plate electrode in the substrate adjacent to a lower portion of the deep trench; forming a node dielectric layer on interior surface of the deep trench; depositing a first conductive layer in the deep trench; recessing the first conductive layer to a first depth in the deep trench; forming a collar oxide layer on sidewall of the deep trench above the first conductive layer; depositing a second conductive layer on the first conductive layer and the collar oxide layer; recessing the second conductive layer to a second depth inside the deep trench; forming a pair of symmetric spacers on sidewall of the deep trench above the second conductive layer in a first direction and exposing a silicon sidewall of the deep trench above the second conductive layer in a second direction, wherein the first direction is substantially orthogonal to the second direction; depositing a third conductive layer on the second conductive layer and on the spacers; and recessing the third conductive layer to a third depth inside the deep trench.