A semiconductor device includes a first insulating substrate and a first semiconductor element joined to the first insulating substrate through the first conductive spacer. The first insulating substrate includes a first insulating layer and a first inner conductive layer disposed at a side of the first insulating layer. The first inner conductive layer includes a surface having a first region and a second region. The second region surrounds the first region and has larger surface roughness than the first region. The first conductive spacer is joined to the first region of the first inner conductive layer through a first junction layer.