Method of fabricating trench cell capacitors on a semocondcutor substrate

DETAILED DESCRIPTION It is hence a primary object of this invention to present a method of fabricating a trench cell capacitor with high aspect ratio precisely.
It is a second object of this invention to present a method of fabricating a trench cell capacitor on a semiconductor substrate without causing damage to the side walls or residual damage in the periphery of the bottom of the trench, and subsequently increasing a breakdown voltage of the dielectric layer and restricting the leakage current between adjacent trench capacitors.
In order to achieve the above objects, this invention presents a method of fabricating trench cell capacitors on a semiconductor substrate which is comprised of following steps: a step of forming a first trench having side walls and a bottom, said side walls are substantially vertical to a surface of the semiconductor substrate of one conductive type and forming an oxide layer on the side walls and the bottom of said first trench, a step of selectively forming a silicon nitride layer on the oxide layer of the side walls of the first trench, and removing the oxide layer on the bottom of the first trench by using the silicon nitride layer as a mask by anisotropic dry etching, a step of removing the silicon nitride layer a step of forming an epitaxial layer of the same conductive type as said semiconductor substrate in the first trench so as to emded the first trench with the epitaxial layer, and a step of removing the oxide film remaining on the side walls of the first trench and forming a second trench having predetermined shaped.
Other features and objects of the present invention will be apparent from the following description taken in connection with the accompanying drawings.