Semiconductor patterning and resulting structures

A method comprising:

• depositing a first oxide hard mask layer over a target layer;
• depositing a second oxide hard mask layer of the first oxide hard mask layer, wherein the second oxide hard mask layer has a greater density than the first oxide hard mask layer, and wherein a density of the second oxide hard mask layer is at least 1.8 g/cm3;
• depositing a mandrel layer over the second oxide hard mask layer;
• etching the mandrel layer to define a plurality of mandrels;
• forming spacers on sidewalls of the plurality of mandrels;
• removing the plurality of mandrels to define openings between the spacers;
• using the spacers as a mask to pattern the first oxide hard mask layer;
• and
• using the first oxide hard mask layer as a mask to pattern the target layer.

A method comprising:

• depositing a first oxide layer over a semiconductor layer;
• depositing a second oxide layer over the first oxide layer, wherein the second oxide layer has a greater density than the first oxide layer, and wherein the second oxide layer is thinner than the first oxide layer;
• forming a plurality of mandrels over the second oxide layer;
• forming spacers on sidewalls of the plurality of mandrels;
• removing the plurality of mandrels to define openings between the spacers, wherein removing the plurality of mandrels etches recesses in the second oxide layer;
• using the spacers as a mask to pattern the first oxide layer;
• and
• using the first oxide layer as a mask to pattern the semiconductor layer.