Patent ID: 6872629

Claim:
A method of forming a memory cell with a single sided buried strap, comprising the steps of: providing a substrate having a trench; forming a trench capacitor at a lower portion of the trench; forming a collar insulating layer on a sidewall of an upper portion of the trench; forming a first conductive layer above the trench capacitor and filling the trench; removing part of the first conductive layer and part of the collar insulating layer to form a remaining first conductive layer and a remaining collar insulating layer in an opening, wherein the opening has a first sidewall and a second sidewall, and a top surface of the remaining collar insulating layer is lower than that of the remaining first conductive layer; performing an angle implantation with fluorine-containing ions on the first sidewall of the opening; performing a thermal oxidation process to form a first oxide layer on the first sidewall and a second oxide layer on the second sidewall, wherein a thickness of the first oxide layer is greater than that of the second oxide layer; removing the second oxide layer to expose the second sidewall; and forming a second conductive layer serving as a buried strap at a bottom of the opening, wherein the second conductive layer is insulated from the first sidewall by the first oxide layer.