Taiwan Semiconductor Manufacturing Comp. Ltd.

R Y Lee

Chue-San Yoo

J H Tsai

A method is provided for forming a shallow trench isolation that has rounded and protected corners by first forming a bird's beak field oxide layer prior to the trench-forming step such that a rounded and protected top corner and a rounded bottom corner of the trench can be formed. The rounded top and bottom corners of the shallow trench opening have a radius of at least 100 .ANG. and a trench depth of not more than 5000 .ANG.. The top corner of the trench opening is protected by the beak portion of the bird's beak against etching in a subsequent oxide dip process before gate formation.

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Hsin-Chu, Taiwan

R Y Lee