An electronic device includes an integrated circuit chip mounted to a heat slug. The heat slug has a peripheral region having first thickness along a first direction, the peripheral region surrounding a recess region (having a second, smaller, thickness along the first direction) that defines a chip mounting surface along a second direction perpendicular to the first direction. The recess region defines side borders and a nook extends into the heat slug along the side borders. An insulating body embeds the integrated circuit one chip and heat slug. Material of the insulating body fills the nook.