According to one embodiment, a semiconductor device includes first to third semiconductor regions and first to third conductors. The second semiconductor region is separated from the first semiconductor region in a first direction. The third semiconductor region is provided between the first and the second semiconductor regions. The third conductor is separated from the third semiconductor region in a second direction intersecting the first direction. The third semiconductor region includes first and second partial regions. The first partial region includes a first metal element, and is amorphous. The second partial region is stacked with the first partial region in the second direction, and is polycrystalline. A first concentration of the first metal element in the first partial region is higher than a second concentration of the first metal element in the second partial region, or the second partial region does not include the first metal element.