Semiconductor devices
A semiconductor device includes active fins on a substrate, a first isolation pattern on the substrate, the first isolation pattern extending on a lower sidewall of each of the active fins, a third isolation pattern including an upper portion extending into the first isolation pattern and a lower portion extending into an upper portion of the substrate, the lower portion contacting the upper portion of the third isolation pattern, and having a lower surface with a width greater than that of an upper surface thereof, and a second isolation pattern extending in the substrate under the third isolation pattern, contacting the third isolation pattern, and having a rounded lower surface.
1. A semiconductor device, comprising:
active fins protruding from an upper surface of a substrate, each of the active fins extending in a first direction substantially parallel to the upper surface of the substrate;
a first isolation pattern on the upper surface of the substrate, the first isolation pattern covering respective lower sidewalls of the active fins in a second direction, the second direction being substantially parallel to the upper surface of the substrate and crossing the first direction;
an isolation structure including:
a third isolation pattern extending in the first isolation pattern; and
a second isolation pattern in a trench that extends in an upper portion of the substrate and has a cross-section of a shape of a portion of a circle or an ellipse, the second isolation pattern comprising:
a lower portion on a bottom of the trench; and
an upper portion on and protruding from an edge portion of the lower portion, the upper portion contacting a lower sidewall of the third isolation pattern;
gate structures each extending in the second direction on upper surfaces of the active fins, an upper surface of the first isolation pattern, and an upper surface of the isolation structure.
2. The semiconductor device of claim 1 , wherein each of the active fins extends in a first direction substantially parallel to the upper surface of the substrate, and the active fins are spaced apart from each other in a second direction substantially parallel to the upper surface of the substrate and intersecting with the first direction, and
wherein the isolation structure extends in the first direction.
3. The semiconductor device of claim 1 , wherein the lower portion of the second isolation pattern has a substantially flat upper surface contacting the third isolation pattern.
4. The semiconductor device of claim 1 , wherein the lower portion of the second isolation pattern has a convex upper surface contacting the third isolation pattern.
5. The semiconductor device of claim 1 , wherein the lower portion of the second isolation pattern has a concave upper surface contacting the third isolation pattern.
6. The semiconductor device of claim 1 , wherein the second isolation pattern comprises a nitride, and the third isolation pattern comprises an oxide.
7. The semiconductor device of claim 1 , wherein the third isolation pattern directly contacts the first isolation pattern.
8. A semiconductor device, comprising:
active fins protruding from an upper surface of a substrate, each of the active fins extending in a first direction substantially parallel to the upper surface of the substrate;
a first isolation pattern on the upper surface of the substrate, the first isolation pattern covering respective lower sidewalls of the active fins in a second direction, the second direction being substantially parallel to the upper surface of the substrate and crossing the first direction;
an isolation structure including:
a second isolation pattern in a trench that extends in an upper portion of the substrate and has a cross-section of a shape of a portion of a circle or an ellipse; and
a third isolation pattern comprising:
an upper portion extending in the first isolation pattern; and
a lower portion beneath and contacting the upper portion of the third isolation pattern, the lower portion partially extending in the second isolation pattern,
gate structures each extending in the second direction on upper surfaces of the active fins, an upper surface of the first isolation pattern, and an upper surface of the isolation structure,
wherein the second isolation pattern extends on a lower surface of the third isolation pattern and on a sidewall of the lower portion of the third isolation pattern.
9. The semiconductor device of claim 8 , wherein each of the active fins extends in a first direction substantially parallel to the upper surface of the substrate, and the active fins are spaced apart from each other in a second direction substantially parallel to the upper surface of the substrate and intersecting with the first direction, and
wherein the isolation structure extends in the first direction.
10. The semiconductor device of claim 8 , wherein a width of the lower portion of the third isolation pattern decreases from bottom to top.
11. The semiconductor device of claim 8 , wherein the lower portion of the third isolation pattern has a substantially flat lower surface contacting the second isolation pattern.
12. The semiconductor device of claim 8 , wherein the lower portion of the third isolation pattern has a concave lower surface contacting the second isolation pattern.
13. The semiconductor device of claim 8 , wherein the lower portion of the third isolation pattern has a convex lower surface contacting the second isolation pattern.
14. The semiconductor device of claim 8 , wherein the second isolation pattern comprises a nitride, and the third isolation pattern comprises an oxide.
15. The semiconductor device of claim 8 , wherein the third isolation pattern directly contacts the first isolation pattern.
16. A semiconductor device, comprising:
active fins protruding from an upper surface of a substrate, the active fins extending in a first direction substantially parallel to the upper surface of the substrate;
a first isolation pattern on the upper surface of the substrate, the first isolation pattern extending on respective lower sidewalls of the active fins in a second direction that is substantially parallel to the upper surface of the substrate and intersects the first direction;
an isolation structure; and
gate structures extending in the second direction on upper surfaces of the active fins, an upper surface of the first isolation pattern, and an upper surface of the isolation structure,
the isolation structure including:
a third isolation pattern extending between adjacent sidewalls of the first isolation pattern; and
a second isolation pattern in a trench that extends in an upper portion of the substrate and has a cross-section of a shape of a portion of a circle or an ellipse, the second isolation pattern comprising:
a lower portion on a bottom of the trench; and
an upper portion on the lower portion, the upper portion contacting a lower portion of the third isolation pattern,
wherein the adjacent sidewalls of the first isolation pattern are free of the second isolation pattern therebetween.
17. The semiconductor device of claim 16 , wherein an interface between the second isolation pattern and the third isolation pattern is confined below the upper surface of the substrate.
18. The semiconductor device of claim 16 , wherein the third isolation pattern directly contacts the first isolation pattern.