Semiconductor device and method of manufacturing a semiconductor device
View Patent ↗A semiconductor device formed in a semiconductor substrate wherein the semiconductor substrate has a trench for isolating elements from each other, the trench has unevenness at the bottom thereof, and an insulator is buried in the trench.
1. A method of manufacturing a semiconductor device comprising:
forming a mask pattern over a semiconductor substrate;
forming a trench having first unevenness in the semiconductor substrate by etching using the mask pattern;
burying an insulator in the trench;
forming a first well having a first conductivity type in the semiconductor substrate,
forming a first transistor in the first well,
forming a second well having a second conductivity type different from the first conductivity type in the semiconductor substrate,
forming a second transistor in the second well,
wherein a bottom of the trench includes a plurality of convex portions extending from the bottom of the trench toward a top of the trench
wherein the trench is located between the first well and the second well,
wherein the first unevenness includes a plurality of projections having a different height downward.
2. The method according to claim 1 , wherein a first difference in height of the first unevenness is greater than a second difference in height of second unevenness formed in a side wall of the trench.
3. The method according to claim 2 , wherein the first difference in height is 30% or less of a depth of the trench.
4. The method according to claim 3 , wherein the first difference in height is 4 nm or more.
5. The method according to claim 2 , wherein the etching is performed using a mixed gas containing chlorine gas and oxygen gas.
6. The method according to claim 5 , wherein the mixed gas further contains a nitrogen gas or a rare gas.
7. The method according to claim 2 , further comprising forming a thermal oxide film over the side wall of the trench before burying the insulator in the trench.
8. The method according to claim 7 , wherein a thickness of the thermal oxide film is less than the first difference in height.
9. The method according to claim 7 , wherein the second difference in height is a half or less of a thickness of the thermal oxide film.
10. The method according to claim 1 , wherein the etching to form the trench is performed using a mixed gas containing chlorine gas, oxygen gas and nitrogen gas.
11. The method according to claim 1 , wherein the trench has a taper angle with respect to a surface of the semiconductor substrate and the taper angle is adjusted by controlling a flow rate of nitrogen in an etching gas.
12. The method according to claim 1 , wherein the trench has a taper angle with respect to a surface of the semiconductor substrate and the taper angle is 80.degree. to 90.degree.
13. A method of manufacturing a semiconductor device comprising:
forming a mask pattern over a semiconductor substrate;
forming a trench having first unevenness in the semiconductor substrate by etching using the mask pattern, the trench having a taper angle with respect to a surface of the semiconductor substrate;
burying an insulator in the trench;
forming a first well having a first conductivity type in the semiconductor substrate,
forming a first transistor in the first well,
forming a second well having a second conductivity type different from the first conductivity type in the semiconductor substrate,
forming a second transistor in the second well,
wherein a bottom of the trench includes a plurality of convex portions extending from the bottom of the trench toward a top of the trench
wherein the trench is located between the first well and the second well,
wherein the taper angle is adjusted by controlling a flow rate of nitrogen in an etching gas.
14. The method according to claim 13 , wherein the first unevenness includes a plurality of projections having a different height downward.