Adjustable method for eliminating trench top corners

An adjustable method for making trenches for a semiconductor integrated circuit device having eliminated top corners comprising the steps of:

• subsequently forming an oxide layer and a silicon nitride layer on the surface of the device substrate of the device, and then forming trenches in the device substrate;
• forming a filling material inside the trenches, and the surface of the filling material inside the trenches being relatively lower than the opening of the trench and further slightly lower than the top surface of the device substrate;
• forming a masking layer on the surface of the silicon nitride layer having openings corresponding to the openings of the trenches, dimension of the masking layer opening being about 110 percent relatively greater than the dimension of the opening of the corresponding trench;
• and
• performing an anisotropic etching procedure against the portions of the device substrate exposed out of the coverage of the masking layer, and the anisotropic etching shaping the trench sidewalls into sloped ones having larger dimension at the opening than at the surface of the filling material inside the trenches.