Patent ID: 6929998
Filing Date: 2005-08-16
Classification: H01L

Abstract:
1. A method for forming a bottle-shaped trench, comprising the steps of: forming a trench in a substrate; filling a lower portion of the trench with a conductive layer surrounded by a doped layer; forming a conformable silicon nitride layer overlying the substrate and an inner surface of an upper portion of the trench to cover the conductive layer and the doped layer; performing a heat treatment on the substrate to form a doping region therein and around the doped layer; anisotropically etching the silicon nitride layer to form a collar silicon nitride layer over the sidewall of the upper portion of the trench; successively removing the conductive layer and the doped layer using the collar silicon nitride layer as a mask to expose the surface of the doping region; partially oxidizing the exposed doping region to form a doped oxide region thereon; removing the doped oxide region to form a bottle-shaped trench; and forming a conformable rugged polysilicon layer in the lower portion of the bottle-shaped trench.