A semiconductor device includes first and second fin-shaped patterns disposed on a substrate and extending in a first direction, first and second channel layers disposed on the first and second fin-shaped patterns, first and second etch stop layers disposed inside the first and second channel layers, first and second gate structures extending in a second direction different from the first direction on the first channel layer with a first recess formed therebetween, third and fourth gate structures extending in the second direction on the second channel layer with a second recess formed therebetween, the first recess having a first width in the first direction and having a first depth in a third direction perpendicular to the first and second directions, the second recess having a second width different from the first width in the first direction, and having a second depth equal to the first depth in the third direction.