Double patterning method of manufacturing select gates and word lines

A double patterning method of manufacturing select gates and word lines, comprising:

• providing a substrate with a target layer formed thereon;
• forming first string patterns on said target layer, wherein said first string patterns extend in a first direction and are spaced apart in a second direction perpendicular to said first direction, and said first string patterns comprises word line patterns with smaller width in said second direction and select gate patterns with larger width in said second direction;
• forming a conformal spacer layer on said first string patterns and said substrate, wherein said conformal spacer layer forms trenches between parts of said first string patterns, and said trenches extend in said first direction and are spaced apart from said first string patterns in said second direction;
• forming a fill layer on said conformal spacer layer, and said fill layer fills up said trenches;
• removing said fill layer outside of said trenches, so that said fill layer remaining in said trenches forms second string patterns, and said second string patterns extend in said first direction and are spaced apart from said first string patterns in said second direction;
• performing an etchback process to remove said conformal spacer layer and said second string patterns above a level of top planes of said first string patterns after removing said fill layer outside of said trenches, so that said first string patterns are exposed and said top planes of said first string patterns, said second string patterns and said conformal spacer layer are flush;
• performing a first etching process to anisotropically remove exposed said conformal spacer layer after said etchback process, so that said first string patterns and said second string patterns constitute target patterns spaced apart from each other on said target layer;
• and
• performing a second etching process using said target patterns as an etching mask to anisotropically remove exposed said target layer, so as to form word lines and select gates.