Method for preventing trench fill erosion

A method for forming a semiconductor device, the method comprising the steps of:

• providing a substrate comprising silicon;
• forming a pad oxide layer over the substrate;
• forming a masking layer comprising nitrogen over the pad oxide later;
• forming an opening through the pad oxide layer, the masking layer, and the substrate to form a trench region within the substrate;
• recessing a sidewall portion and a top portion of the masking layer to form a recessed region spaced away from and around a top portion of the trench region;
• filling the trench region, including the recessed region, with a dielectric material;
• polishing the dielectric material to planarize a top portion of the dielectric material, the polishing leaving planarized dielectric material within the trench region and the recessed region.

A method for forming a semiconductor device, the method comprising the steps of:

• providing a silicon-based substrate;
• forming a pad oxide layer over the substrate;
• forming a masking layer comprising nitrogen over the pad oxide layer;
• forming a protection layer over the masking layer;
• forming an opening through the pad oxide layer, the masking layer, the protection layer, and the substrate to form a trench region in the substrate, the trench region region having a sidewall;
• recessing a sidewall portion of the masking layer to form a recessed region in the masking layer, wherein the recessed region has a sidewall spaced from the sidewall of the trench region and wherein a top portion of the masking layer is substantially protected from removal by the presence of the protection layer;
• filling the trench region, including the recessed region, with a dielectric material;
• polishing the dielectric material to planarize a top portion of the dielectric material while leaving dielectric material within the trench region and the recessed region.

A method for forming a trench in a substrate, the method comprising the steps of:

• forming a masking layer over the substrate;
• forming an opening in the masking layer to form a patterned masking layer;
• etching a trench region in the substrate having a sidewall aligned to the opening;
• isotropically etching the patterned masking layer to recess the opening relative to the sidewall of the trench region;
• and
• filling the trench region and the opening after the patterned masking layer has been isotropically etched.