Patent ID: 8110475

Claim:
A method for forming a memory device, comprising: providing a substrate; forming a capacitor in the substrate or overlying the substrate, wherein the capacitor has a C-shaped pattern at a cross section parallel to a surface of the substrate; and forming a word line on the substrate; wherein the capacitor is a C-shaped deep trench capacitor, and the step of forming the C-shaped deep trench capacitor comprises: patterning the substrate to form a C-shaped deep trench; and fabricating the C-shaped deep trench capacitor according to the C-shaped deep trench; wherein the step of fabricating the C-shaped deep trench capacitor according to the C-shaped deep trench comprises: forming a capacitor at a lower portion of the C-shaped deep trench and a first polysilicon layer is formed on the capacitor in the C-shaped deep trench; forming a collar dielectric layer covering an upper sidewall of the C-shaped deep trench; forming a second polysilicon layer on the capacitor in the C-shaped deep trench; and selectively opening a portion of the collar dielectric layer neighboring a central portion of an inner edge of the C-shaped deep trench; wherein the method for forming a memory device further comprises: performing at least one implanting process to dope a portion of the substrate neighboring the central portion of the inner edge of the C-shaped deep trench for forming a buried strap; forming a third polysilicon layer in the C-shaped deep trench and on the second polysilicon layer; and forming an insulating layer on the third polysilicon layer in the C-shaped deep trench.