SEMICONDUCTOR DEVICE AND METHOD OF FABRICATING THE SAME

Disclosed are semiconductor devices and methods of fabricating the same. The semiconductor device comprises a substrate having a trench, a gate dielectric layer covering a surface of the trench, a gate electrode filling a lower portion of the trench, a capping pattern on the gate electrode in the trench, and a work function control pattern between the gate electrode and the capping pattern in the trench. The gate dielectric layer comprises a first segment having a first thickness between the gate electrode and the trench and a second segment having a second thickness between the capping pattern and the trench. The second thickness is less than the first thickness.