US Patent 7749912 Method for fabricating bulb-shaped recess pattern

A method for fabricating a bulb-shaped recess pattern includes: forming an etch barrier layer over a substrate; forming a hard mask pattern in which a first polymer is attached to sidewalls of the hard mask pattern over the etch barrier layer; sequentially etching the etch barrier layer and the substrate to form a recess pattern in which a second polymer is attached to sidewalls of the recess pattern; removing the first and second polymers and the hard mask pattern; forming a plurality of spacers exposing a bottom portion of the recess pattern; and etching the exposed bottom portion of the recess pattern to form a ball pattern.