Semiconductor device

A semiconductor device is provided. The semiconductor device includes a substrate including an active pattern, a gate electrode extending in a first direction and crossing the active pattern which extends in a second direction, a separation structure crossing the active pattern and extending in the first direction, a first gate dielectric pattern disposed on a side surface of the gate electrode, a second gate dielectric pattern disposed on a side surface of the separation structure, and a gate capping pattern covering a top surface of the gate electrode. A level of a top surface of the separation structure is higher than a level of a top surface of the gate capping pattern.