An electronic device includes a substrate wafer made of an insulating material and having an electrical connection network. An integrated circuit chip is mounted to a top side of the substrate wafer. The substrate wafer contains an internal duct. The duct is formed by a covered trench located in the top side of the substrate wafer. The trench contains a thermally conductive material, for example being a fluid. Openings in the top side of the substrate wafer that are offset from the trench permit the making of an electrical connection between the integrated circuit and the electrical connection network.