Patent ID: 6964898

Claim:
A method for fabricating a trench capacitor, comprising: providing a substrate; etching the substrate to form a first trench recess with a first depth; depositing a spacer layer on interior surface of the first trench recess; anisotropic etching the spacer layer to form a spacer on sidewall of the first trench recess, and through the first trench recess, continuing to etch the substrate so as to form a second trench recess with a second depth; performing an oxidation process to form a silicon oxide layer on interior surface not covered by the spacer within the second trench recess; anisotropic etching the silicon oxide layer to form a self-aligned collar oxide layer on sidewall of the second trench recess, and through the second trench recess, continuing to etch the substrate to form a deep trench recess with a third depth; doping the deep trench recess to form a diffusion region at a lower portion of the deep trench recess, the diffusion region serving as a first electrode of the trench capacitor; forming a capacitor dielectric layer under the self-aligned collar oxide layer on interior surface of the deep trench recess; filling the deep trench recess with a first conductive layer serving as a second electrode of the trench capacitor; and recess etching the first conductive layer to form a first conductive stud within the deep trench recess, the first conductive stud has a top surface that is lower than the surface of the substrate, but is higher than the self-aligned collar oxide layer.