A semiconductor device may include an active pattern, a capacitor contact structure electrically connected to the active pattern, and a capacitor structure electrically connected to the capacitor contact structure. The capacitor structure may include a first lower electrode and a second lower electrode that are adjacent to each other, a supporter supporting the first and second lower electrodes, a capacitor insulating layer covering the first and second lower electrodes, and an upper electrode on the capacitor insulating layer. The supporter may include a first supporter curved sidewall connected to the first lower electrode and the second lower electrode, and the upper electrode may include an intervening electrode portion enclosed by the supporter. The first supporter curved sidewall may be convex toward the intervening electrode portion.