Patent ID: 6800535
Filing Date: 2004-10-05
Classification: H01L

Abstract:
A method for forming bottle-shaped trenches, suitable for use in a dynamic random access memory (DRAM), comprising:providing a substrate; forming a hard mask having openings on the substrate; etching the substrate through the openings to form trenches with an upper portion and a lower portion; conformally forming an isolated layer in the trenches and on the hard mask; forming a shield layer in the lower portion of the trenches; removing parts of the isolated layer which is not covered by the shield layer to expose a surface of the upper portion of the trenches; forming a protective layer on sidewells of the upper portion of the trenches; removing the shield layer to expose the isolated layer in the lower portion of the trenches; removing the isolated layer to expose the substrate of the lower portion of the trenches; and etching the substrate of the lower portion of the trenches using the protective layer as a mask to form bottle-shaped trenches.