Patent ID: 7419872

Claim:
A method for preparing a trench capacitor structure, comprising the steps of: forming at least one trench in a substrate; forming a capacitor in a lower portion of the trench, wherein the capacitor comprises a first dielectric layer covering an inner sidewall of the trench and a top electrode filling the lower portion of the trench; forming a collar insulation layer on an upper inner sidewall of the trench; forming a first conductive block in the collar insulation layer; forming a second conductive block with dopants on the first conductive block; performing a first thermal treating process to diffuse the dopants from the second conductive block into the substrate on an upper outer surface of the trench; wherein the collar insulation layer covers the first dielectric layer above the top electrode; and performing a wet etching process to remove the collar insulation layer and the first dielectric layer above the first conductive block.