A semiconductor device includes a substrate having first and second principal surfaces, and a semiconductor chip disposed on the first principal surface. The substrate includes a first conductor layer disposed on the first principal surface, a second conductor layer disposed on the second principal surface, at least one third conductive layer between the first conductive layer and the second conductive layer, a detection interconnection disposed in either the first conductive layer or the third conductive layer, and first and second pads disposed on the second conductive layer and connected to the detection interconnection. The detection interconnection is not part of signal interconnections that are used during operation of the semiconductor chip and is not electrically connected to any circuit of the semiconductor chip.