Semiconductor device having trench isolation

Abstract

A semiconductor device with trench isolation is provided to restrain reverse narrow-channel effect and to obtain improved reliability from a gate insulating layer by forming a protrusion with a double insulating layer structure at both upper sidewalls of a burial insulating layer. A trench(2) is formed in a semiconductor substrate(1). A burial insulating layer(3) is filled in the trench. At this time, an upper surface of the burial insulating layer is higher than that of the substrate, so that both sidewalls of the burial insulating layer are partially exposed to the outside. A protrusion(3b2,3c) is formed at both exposed sidewalls of the burial insulating layer by stacking at least two insulating layers with each other.

Description

technical field [0001] The present invention relates to a semiconductor device with trench isolation, and more particularly to a semiconductor device with trench isolation for electrically isolating a semiconductor element from other semiconductor elements. Background technique [0002] In recent years, with the refinement of patterns in semiconductor devices, as an element isolation structure for electrically isolating semiconductor elements such as field effect transistors from other semiconductor elements, a structure called STI (Shallow Trench Isolation: Shallow Trench Isolation) is generally used. . Such STIs are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2002-100671, 2002-93900, and 11-67892. [0003] Such an STI is formed, for example, by the following steps. [0004] First, a thermal oxide film and a silicon nitride film are formed on a semiconductor substrate, and a photoresist pattern is formed on the silicon nitride film. Using the ph...

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Problems solved by technology

If the gate electrode is formed to extend through the gate insulating layer on such a depressed portion, the reverse narrow channel effect will occur, and the reliability of the gate insulating layer will also deteriorate, making it difficult to manufacture high-performance transistors or flash memory.

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