Method of manufacturing semiconductor device having trench type element isolation regions

Abstract

Trench isolation regions of different depths are formed through a simple manufacturing process, and reliability of a semiconductor device is increased. Trenches ( ) of different widths are formed on a semiconductor substrate ( ) on which an underlying film ( ) such as a silicon oxide film and a mask material ( ) such as a silicon nitride film are formed. Then, an insulating film such as a silicon oxide film is deposited over the entire surface to such a degree that the narrower trench ( ) is filled up. At this time, the wider trench ( ) has an unfilled space in its central portion. a The surface of the substrate ( ) is then vertically etched back until it is exposed in the trench . With insulating films ( ) in the trenches ( ) as a mask, the surface of the substrate ( ) is anisotropically etched vertically to form a deeper bottom ( ) in the trench ( ). After that, the surface is planarizedby depositing an insulating film in the unfilled space of the trench ( ).