| 摘要 |
PROBLEM TO BE SOLVED: To fabricate stably a MOS transistor which does not cause hump phenomenon by providing a method for forming a trench element isolating region that ensures high reliability and high yield. SOLUTION: A pad insulating layer 2 and an oxide mask layer 3 are patterned on a surface of a silicon substrate 1, and the surface of the substrate 1 is masked by the oxide mask layer 3 and selectively heat-oxidized to form a LOCOS oxide film having a bird's beak 5. Then a trench 6 is formed on the silicon substrate 1 by dry-etching both the LOCOS oxide film and the silicon substrate 1 underneath thereof utilizing the oxide mask layer 3 as an etching mask. Then an embedding insulating film 8 is deposited to fully embed the trench, and the deposited film is chemically mechanically polished until a trench element isolating area is formed. The oxide mask layer 3 works as a polish stopper layer.
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