Semiconductor memory structure and method for forming the same

A method for forming a semiconductor memory structure, comprising:

• forming a hard mask layer over a semiconductor substrate;
• etching the hard mask layer to form a plurality of first mask patterns and a plurality of second mask patterns;
• transferring the plurality of first mask patterns and the plurality of second mask patterns to the semiconductor substrate to form a plurality of semiconductor blocks;
• thinning down the plurality of second mask patterns, wherein a thickness of the plurality of second mask patterns is less than a thickness of the plurality of first mask patterns after thinning down the plurality of second mask patterns;
• forming a first capping layer that extends laterally over the plurality of first mask patterns and the plurality of second mask patterns;
• and
• etching the first capping layer and the plurality of second mask patterns to form a plurality of contact openings.