A semiconductor device includes a semiconductor substrate, an element isolation film, and a fin having side surfaces facing each other in a first direction of an upper surface and a main surface connecting the facing side surfaces and extending in a second direction orthogonal to the first direction. The device further includes a control gate electrode arranged over the side surface via a gate insulation film and extending in the first direction, and a memory gate electrode arranged over the side surface via another gate insulation film having a charge accumulation layer and extending in the first direction. Furthermore, an overlap length by which the memory gate electrode overlaps with the side surface is smaller than an overlap length by which the control gate electrode overlaps with the side surface in the direction orthogonal to the upper surface.