Method for selectively etching portions of a layer of material based upon a density or size of semiconductor features located thereunder

A method for manufacturing a semiconductor device, comprising:

• forming active device regions within a substrate using a first patterned masking layer, the active device regions separated from one another with trenches;
• forming a layer of dielectric material over the active device regions and within the trenches;
• selectively etching portions of the layer of dielectric material based upon a density or size of the active device regions or the trenches and using a second patterned masking layer, wherein the second patterned masking layer is not a substantially reverse pattern of the first patterned masking layer;
• polishing remaining portions of the layer of dielectric material after selectively etching;
• and
• forming gate structures over one or more of the active device regions, wherein the gate structures each includes a gate dielectric and a gate electrode.