There is provided a semiconductor device having reduced contact resistance and enhanced performance. The semiconductor device includes a substrate, a first active pattern spaced apart from the substrate and extending in a first direction, and including a first two-dimensional semiconductor material, a first gate electrode extending in a second direction intersecting the first direction on the substrate, and through which the first active pattern penetrates, and a first source/drain contact which includes a first contact insertion film and a first filling metal film sequentially stacked on a side surface of the first gate electrode, and is connected to the first active pattern, wherein the first contact insertion film at least partially surrounds a lower surface, a side surface and an upper surface of an end portion of the first active pattern, and the first active pattern and the first contact insertion film form an ohmic contact.