A semiconductor device according to an embodiment includes a first substrate including a first insulating layer, a first conductive layer provided in the first insulating layer, a first metal layer provided in the first insulating layer, and a second metal layer provided between the first metal layer and the first conductive layer, a linear expansion coefficient of the second metal layer being higher than that of the first metal layer; and a second substrate including a second insulating layer, and a third metal layer provided in the second insulating layer, in contact with the first metal layer. The second substrate contacts with the first substrate.