| CPC H01L 21/823412 (2013.01) [H01L 21/3065 (2013.01); H01L 21/308 (2013.01); H01L 21/3086 (2013.01); H01L 21/31116 (2013.01); H01L 21/31144 (2013.01); H01L 21/823431 (2013.01); H01L 21/823807 (2013.01); H01L 27/0886 (2013.01); H01L 27/0924 (2013.01); H01L 29/0657 (2013.01); H01L 29/0692 (2013.01); H01L 29/1025 (2013.01); H01L 29/1037 (2013.01); H01L 29/66795 (2013.01); H01L 29/785 (2013.01)] | 20 Claims | 

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               16. A method, comprising: 
            forming a first patterning layer on a substrate; 
                forming a second patterning layer on the first patterning layer; 
                etching the second patterning layer to form a first plurality of trenches and a second plurality of trenches, wherein a first width of the first plurality of trenches is less than and a second width of the second plurality of trenches; 
                etching the first patterning layer to increase a depth of the first plurality of trenches and the second plurality of trenches; and 
                selectively etching the first plurality of trenches and the second plurality of trenches, wherein a first horizontal etching rate in the first plurality of trenches is lower than a second horizontal etching rate in the second plurality of trenches. 
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