Patent ID: 6991994
Filing Date: 2006-01-31
Classification: H01L

Abstract:
1. A method for forming a trench having rounded corners in a semiconductor device, the method comprising: providing a semiconductor substrate; forming a first pad oxide layer, a first silicon nitride layer, and a first oxide layer on the semiconductor substrate sequentially; removing portions of the first oxide layer, the first silicon nitride layer, the first pad oxide layer, and the semiconductor substrate to form at least one trench; removing portions of the first oxide layer, the first silicon nitride layer, and the first pad oxide layer in the trench above an upper corner of the semiconductor substrate in the trench, the semiconductor substrate including a lower corner at a bottom of the trench; forming a second pad oxide layer in the trench; forming a second silicon nitride layer on the second pad oxide layer and the first oxide layer; removing portions of the second silicon nitride layer to expose the second pad oxide layer on the corners and the bottom of the trench; forming a thermal oxide layer on the second pad oxide layer exposed by removing the portions of the second nitride layer; and removing the second silicon nitride layer, the thermal oxide layer, and the second pad oxide layer.