| 摘要 |
PROBLEM TO BE SOLVED: To prevent the generation of polishing variations in an STI forming method by so forming isolation trenches as to pass them through a stopper layer on a semiconductor substrate, and by forming an insulation film as filling the isolation trenches with it to flatten it then, and moreover, by removing thereafter the insulating film until its surface reaches the stopper layer to further remove the stopper layer. SOLUTION: On the diffused layer region of a semiconductor substrate 1, a nitride film 3 to be used as a stopper is formed via a pad oxide film 2, and trenches 5 used as isolation trenches for a shallow trench isolation(STI) are so formed to reach the semiconductor substrate 1 by passing them through the nitride film 3. While filling the trenches 5 with an insulation film 4, it is formed on the substrate 1. Then, the steps formed by fine and steep protruding portions 6 when forming the insulation film 4 are flattened by a first polishing method, to remove the insulation film 4 by a second polishing method different from the first one until its surface reaches the nitride film 3. Furthermore, the nitride film 3 is removed by an etching to form the STI.
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