Semiconductor device and method of fabricating the same

1. A semiconductor device, comprising:

a substrate that includes a peripheral region and a logic cell region;

a device isolation layer that defines a first active pattern on the peripheral region, a second active pattern on the logic cell region, and a third active pattern on the logic cell region; and

first, second, and third transistors on the first, second, and third active patterns, respectively,

wherein each of the first, second, and third transistors includes a gate electrode, a gate spacer that covers a sidewall of the gate electrode, a source pattern on a first side of the gate electrode and a drain pattern on a second side of the gate electrode opposite to the first side,

wherein the second active pattern includes a semiconductor pattern in an upper portion of the second active pattern, wherein the semiconductor pattern overlaps the gate electrode,

wherein at least a portion of a top surface of the device isolation layer is located at a higher level than a top surface of the second active pattern and a top surface of the third active pattern, and

wherein a profile of the top surface of the device isolation layer includes two or more convex portions between the second active pattern and the third active pattern.

2. The semiconductor device of claim 1 , wherein the two or more convex portions include a first convex portion and a second convex portion,

wherein the first convex portion is adjacent to the second active pattern,

wherein the second convex portion is adjacent to the third active pattern, and

wherein the second convex portion is located at a higher level than the first convex portion.

3. The semiconductor device of claim 1 , wherein, between the second active pattern and the third active pattern, a maximum height difference between the top surface of the device isolation layer and the top surface of the third active pattern is in a range from about 200 Å to about 400 Å.

4. The semiconductor device of claim 1 , wherein the semiconductor device further comprises:

a first gate dielectric layer provided between the first active pattern and the gate electrode of the first transistor; and

a second gate dielectric layer provided between each of the second and third active patterns and the gate electrode of each of the second and third transistors, wherein

a thickness of the first gate dielectric layer is greater than a thickness of the second gate dielectric layer.

5. The semiconductor device of claim 4 , wherein

the thickness of the first gate dielectric layer is in a range of about 200 Å to about 500 Å, and

the thickness of the second gate dielectric layer is in a range of about 20 Å to about 50 Å.

6. The semiconductor device of claim 4 , wherein each of the second and third transistors further includes a high-k dielectric layer between the gate electrode and the second gate dielectric layer and between the gate electrode and the gate spacer,

wherein the gate spacer covers a sidewall of the high-k dielectric layer and a sidewall of the second gate dielectric layer.

7. The semiconductor device of claim 1 , wherein a portion of the gate spacer included in each of the second and third transistors is in contact with the top surface of the device isolation layer.

8. The semiconductor device of claim 1 , wherein a width of the gate electrode in the first transistor is greater than a width of the gate electrode in each of the second and third transistors.

9. The semiconductor device of claim 1 , wherein the semiconductor pattern includes silicon germanium (SiGe).