A semiconductor device includes: a lower wiring including: a lower filling film, which extends in a first direction and includes a first portion having a first width in the first direction and a second portion, having a second width smaller than the first width in the first direction, on the first portion; and a lower barrier film which is disposed on a side wall and a bottom surface of the first portion, and is not disposed on a side wall of the second portion in a cross-sectional view of the first direction; and an upper wiring structure including: an upper via connected to the lower wiring; and an upper wiring extending in a second direction intersecting the first direction on the upper via, wherein the upper wiring structure further includes an upper barrier film, and an upper filling film in a trench defined by the upper barrier film, each of the upper via and the upper wiring comprises the upper barrier film and the upper filling film, and the upper via is not separated from the upper wiring by the upper barrier film, and is separated from the second portion of the lower filling film by the upper barrier film.