A semiconductor device comprising: a substrate including a first surface and a second surface opposite to each other in a first direction (D1); a first active pattern (AP1) disposed on the first surface of the substrate and extending in a second direction (D2) intersecting the first direction (D1); a field insulating film disposed on the first surface of the substrate and covering sidewalls of the first active pattern (AP1); a power rail (PR) disposed on the second surface of the substrate and extending in the second direction (D2); a via trench (PVA_T) disposed on one side of the first active pattern (AP1) and penetrating through the field insulating film ; a power rail via (PVA) filling the via trench (PVA_T) and connected to the power rail (PR); and a via insulating liner disposed between sidewalls of the via trench (PVA_T) and sidewalls of the power rail via (PVA),wherein the power rail via (PVA) includes: a first sub-film (PVA_1) formed as a single film and filling a lower portion of the via trench (PVA_T); and a second sub-film (PVA_2) disposed at an upper portion of the via trench (PVA_T) on the first sub-film (PVA_1), wherein the second sub-film (PVA_2) includes a filling film (PVA_2b) and a barrier film (PVA_2a) disposed between sidewalls of the filling film (PVA_2b) and the via insulating liner , and wherein sidewalls of the first sub-film (PVA_1) are in contact with the via insulating liner . a substrate including a first surface and a second surface opposite to each other in a first direction (D1); a first active pattern (AP1) disposed on the first surface of the substrate and extending in a second direction (D2) intersecting the first direction (D1); a field insulating film disposed on the first surface of the substrate and covering sidewalls of the first active pattern (AP1); a power rail (PR) disposed on the second surface of the substrate and extending in the second direction (D2); a via trench (PVA_T) disposed on one side of the first active pattern (AP1) and penetrating through the field insulating film ; a power rail via (PVA) filling the via trench (PVA_T) and connected to the power rail (PR); and a via insulating liner disposed between sidewalls of the via trench (PVA_T) and sidewalls of the power rail via (PVA),wherein the power rail via (PVA) includes: a first sub-film (PVA_1) formed as a single film and filling a lower portion of the via trench (PVA_T); and a second sub-film (PVA_2) disposed at an upper portion of the via trench (PVA_T) on the first sub-film (PVA_1), wherein the second sub-film (PVA_2) includes a filling film (PVA_2b) and a barrier film (PVA_2a) disposed between sidewalls of the filling film (PVA_2b) and the via insulating liner , and a first sub-film (PVA_1) formed as a single film and filling a lower portion of the via trench (PVA_T); and a second sub-film (PVA_2) disposed at an upper portion of the via trench (PVA_T) on the first sub-film (PVA_1), wherein the second sub-film (PVA_2) includes a filling film (PVA_2b) and a barrier film (PVA_2a) disposed between sidewalls of the filling film (PVA_2b) and the via insulating liner , and wherein sidewalls of the first sub-film (PVA_1) are in contact with the via insulating liner . <EOS>