Semiconductor device

A semiconductor device, comprising:

• a substrate including an active pattern extending in a first direction;
• a device isolation layer, which is provided on the substrate to define the active pattern;
• a separation structure crossing the active pattern and extending in a second direction crossing the first direction;
• a gate electrode crossing the active pattern and extending in the second direction;
• a first gate spacer disposed on a side surface of the gate electrode;
• and
• a first gate dielectric pattern interposed between the gate electrode and the first gate spacer,
• wherein an upper portion of the active pattern comprises a first recess,
• an upper portion of the device isolation layer comprises a second recess, and
• the separation structure fills the first and second recesses.