A semiconductor device is provided as follows. A first nanowire is disposed on a substrate. The first nanowire is extended in a first direction and spaced apart from the substrate. A gate electrode surrounds a periphery of the first nanowire. The gate electrode is extended in a second direction intersecting the first direction. A gate spacer is formed on a sidewall of the gate electrode. The gate spacer includes an inner sidewall and an outer sidewall facing each other. The inner sidewall of the gate spacer faces the sidewall of the gate electrode. An end portion of the first nanowire is protruded from the outer sidewall of the gate spacer. A source/drain epitaxial layer is disposed on at least one side of the gate electrode. The source/drain is connected to the protruded end portion of the first nanowire.