MANUFACTURE OF SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To enable flatenning the surface of a substrate without reducing the thickness of an oxide film in an element isolation region having a trench structure, and restrain deterioration of element characteristic which is to be caused by dishing. SOLUTION: A first silicon nitride film 3 is formed on a silicon substrate 1. First island-shaped regions 1a and a second island-shaped region 1d are formed by etching, first trenches 1b are formed between the first island-shaped regions 1a, and a second trench 1c is formed between the first island-shaped region 1a and the second island-shaped region 1d. A silicon oxide film 4 is deposited on the whole surface so as to fill the first trenches 1b and the second trench 1c. A second silicon nitride film 5 is formed on the whole surface. The upper surface of the first silicon nitride film 3 on the second island-shaped region 1d is expoed by a CMP method using first slurry. The upper surface of the first silicon nitride film 3 on the first island-shaped regions 1a is exposed by a CMP method using second slurry. A specified amount of the silicon oxide film 4 is etched.