Disclosed are a semiconductor device and a method of fabricating the same. The semiconductor device includes a substrate including a first region and a second region; an active region on the first region and a peripheral active region on the second region; a channel pattern on the active region; a peripheral channel pattern on the peripheral active region; a first gate electrode on the channel pattern; and a second gate electrode on the peripheral channel pattern. A linewidth of the second gate electrode is larger than a linewidth of the first gate electrode, and a difference in height between the first and second gate electrodes is smaller than about 10 nm, and a top surface of the second gate electrode has a doubly-concave shape.