A method for forming a square
oxide structure or a square floating gate without a
rounding effect at its corners. A first
dielectric layer is formed on a pad layer for a square
oxide structure or a polysilicon layer overlying a
gate oxide layer for a floating gate, and a second
dielectric layer is formed on the first
dielectric layer. The second
dielectric layer is patterned to form parallel openings in a first direction using a first photosensitive
mask. A second photosensitive
mask, having a plurality of parallel openings in a second direction perpendicular to the first direction is formed over the second
dielectric layer and the first
dielectric layer. The first dielectric layer is etched through square openings where the openings in the second photosensitive
mask and the openings in the second dielectric layer intersect, thereby forming square openings in the first dielectric layer. The second photosensitive mask and the second dielectric layer are removed. The square
oxide structure is completed by
etching a trench in the
semiconductor structure and forming an STI or
LOCOS. The square floating gate is completed by growing polysilicon oxide structures in the square openings in the first dielectric layer and removing the first dielectric layer to form a pattern of openings therebetween, and
etching the polysilicon layer through the pattern of openings between the polysilicon oxide structures forming square floating gate polysilicon regions under the polysilicon oxide hard masks.