Patent ID: 7670901

Claim:
A method comprising: (a) forming a trench in a substrate, said trench having sidewalls and a bottom, said trench having an upper region adjacent to a top surface of said substrate and a lower region adjacent to said bottom of said trench; after (a), (b) forming a first layer on said sidewalls and bottom of said trench, forming a second layer on said first layer, forming a third layer on said second layer and forming a fourth layer on said third layer; after (b), (c) removing said fourth layer from said upper region, said fourth region remaining in said bottom region; after (c), (d) forming a fifth layer on said third layer in said upper region; after (d), (e) removing said fourth layer from said lower region; after (e), (f) removing said third layer from said lower region, said first, second and third layers remaining in said upper region; after (f), (g) simultaneously removing said fifth layer from said upper region and said second layer from said lower region, said first region remaining in said lower region, said first, second and third layers remaining in said upper region; after (g), (h) removing said first layer from said lower region, said first and second layers remaining in said upper region; after (h), (i) forming an oxidized layer of said substrate in said bottom region of said trench, said first second and third layer remaining in said upper region; and after (i), (j) simultaneously removing said third layer from said upper region and said oxidized layer of said substrate from said bottom region to form a bottle region of said trench, said first and second layers remaining in said upper region, a cross-sectional area of said bottle region greater than a cross-sectional area of said upper region.