Semiconductor structure and methods of forming the same

A method of forming a semiconductor structure, comprising:

• forming a dielectric layer over a semiconductor substrate;
• forming a hard mask structure on the dielectric layer;
• forming mandrel patterns on the hard mask structure;
• forming a first spacer layer to cover the mandrel patterns within a first region and a second region;
• thinning a portion of the first spacer layer within the second region, thereby forming a partially thinned first spacer layer;
• etching back the partially thinned first spacer layer to form a spacer mask on sidewalls of the mandrel patterns;
• removing the mandrel patterns;
• and
• patterning the hard mask structure and the dielectric layer to transfer a pattern of the spacer mask into the hard mask structure and the dielectric layer.

A semiconductor structure, comprising:

• a substrate;
• a dielectric layer disposed on the substrate, comprising a first dielectric portion and a second dielectric portion;
• and
• a conductive layer laterally aside the dielectric layer, comprising:
• first conductive lines spaced apart by the first dielectric portion therebetween;
• and
• second conductive lines spaced apart by the second dielectric portion therebetween,
• wherein a first spacing between the first conductive lines is different from a second spacing between the second conductive lines.