Patent ID: 8524546
Filing Date: 2013-09-03
Classification: H01L

Abstract:
1. A method comprising: forming trench isolation regions in a silicon layer of a substrate to define a first silicon region and a second silicon region bounded by said trench isolation regions; patterning a first hardmask layer to form a first hardmask island on said first silicon region and a second hardmask island on said second silicon region; patterning a second hardmask layer on said first silicon region and said first hardmask island and on said second silicon region and said second hardmask island; removing said second hardmask layer from said second silicon region and said second hardmask island to provide second exposed areas of said second silicon region; patterning first and second mandrels over said first silicon region and said second silicon region; forming a third hardmask layer over said substrate; removing said first and second mandrels to form openings in said third hardmask layer; etching said second exposed areas of said second silicon region to form second trenches to a second depth in said second silicon region; removing said second hardmask layer from said first silicon region and said first hardmask island to provide first exposed areas of said first silicon region; and simultaneously etching said first exposed areas of said first silicon region to form first trenches to a first depth in said first silicon region and further etching said second trenches to a third depth, said third depth being greater than said first depth.