A semiconductor device encompasses a cooler made of ceramics, having a first main face and a second main face, being parallel and opposite to the first main face, defined by two opposite side faces perpendicular to the first and second main faces, a plurality of conductive-pattern layers delineated on the first main face, a semiconductor chip mounted on the first main face via one of the plurality of conductive-pattern layers, and a seal member configured to seal the semiconductor chip.