A semiconductor device includes a first source wiring substructure connected to a plurality of source doping region portions of a transistor structure, and a second source wiring substructure connected to a plurality of source field electrodes located in a plurality of source field trenches extending into a semiconductor substrate. A contact wiring portion of the first source wiring substructure and a contact wiring portion of the second source wiring substructure are located in a wiring layer of a layer stack located on the semiconductor substrate. The contact wiring portion of the first source wiring substructure and the contact wiring portion of the second source wiring substructure each have a lateral size sufficient for a contact for at least a temporary test measurement. The wiring layer including the contact wiring portions is located closer to the substrate than any ohmic electrical connection between the first and the second source wiring substructures.