Patent ID: 8581322

Claim:
A method for making a nonvolatile memory device, comprising steps of: forming a first conductive structure, wherein the first conductive structure has a first top portion; converting the first top portion into a second top portion having a domed surface; forming a workpiece, wherein the workpiece includes a first conductive layer with a thickness, a hard mask portion and a planarized dielectric structure, the hard mask portion is disposed on the first conductive layer, the first conductive layer includes a first top surface, a top edge conductive portion and the first conductive structure, the planarized dielectric structure includes a first dielectric portion and is coupled to the first conductive layer and the hard mask portion, and the first top portion has a sub-portion with an exposed edge-trimmed surface; exposing the top edge conductive portion and a remaining dielectric structure of the planarized dielectric structure by removing the first dielectric portion, wherein the remaining dielectric structure includes an exposed top surface and a second dielectric portion; exposing the first conductive structure being a remaining conductive structure by removing the hard mask portion on a condition that the exposed top surface remains to be lower than the first top surface for a specific distance less than the thickness and the hard mask portion is removed to simultaneously remove the top edge conductive portion; transforming the sub-portion into a first oxide layer for converting the first top portion into a third top portion by applying a low temperature oxidation process to the exposed edge-trimmed surface, wherein the first oxide layer covers the third top portion; and converting the third top portion into the second top portion by removing the first oxide layer and the second dielectric portion.