Method of reducing trench aspect ratio

摘要

A method of reducing trench aspect ratio. A trench is formed in a substrate. Using HDP-CVD, a conformal first oxide layer is formed on a surface of the trench. A conformal first nitride layer is formed on the first oxide layer. Part of the first nitride layer is removed to cause the first nitride layer to be lower than a top surface of the substrate. Using a BOE solution, the first nitride layer and part of the first oxide layer are removed to leave a remaining first oxide layer on the lower portion of the surface of the trench. Thus, the trench aspect ratio is reduced.