ISOLATION OF TRENCH ELEMENT USING SILICON-RICH SILICON NITRIDE FILM

摘要

PROBLEM TO BE SOLVED: To provide a method for isolating a trench element using an Si-rich silicon nitride film. SOLUTION: A mask layer 16 which includes an Si-rich silicon nitride film 14A is formed on a semiconductor substrate 10. For the formation of the mask layer, a pad oxide film 12a and the Si-rich silicon nitride film are sequentially formed on the semiconductor substrate. Trenches are made in the semiconductor substrate using the mask layer as an etching mask. A thermal oxidation film 20 is formed on the inner walls of the trenches. An insulating layer 30 for embedding the trenches is formed inside the trenches and on the mask layer. The trench-embedding insulating layer is subjected to a heat treatment. The amount of silicon contained in the Si-rich silicon nitride film is greater than that in Si3 N4 . Thereby a surface of an active region of the semiconductor substrate can be prevented basically from being damaged by stresses in the silicon nitride film, thus insulating characteristics of a gate oxide film in a transistor manufactured in subsequent steps can be prevented from being deteriorated.