Correlation between gate oxide reliability and the profile of the trench top corner in Shallow Trench Isolation (STI)

In order to develop a Shallow Trench Isolation (STI) which does not have trench corner induced degradation of the gate oxide, its integrities were evaluated with rounded, non-rounded top corner, and an addition of CVD SiO/sub 2/ spacer. In the experiment, we found that the rounded and SiO/sub 2/ spacered STI showed the best result meaning no harmful influence of the corner to the gate oxide integrity. Also, etch-back processes of the filled CVD SiO/sub 2/ were modified to eliminate the degradation of the gate oxide by a stress concentration at top corner kinks.