An insulated heat dissipation substrate including: a ceramic substrate; and a conductor layer bonded onto at least one of main surfaces of the ceramic substrate, wherein the conductor layer includes an upper surface, a lower surface bonded to the ceramic substrate, and a side surface connecting the upper surface with the lower surface wherein, a tip of the upper surface recedes in the normal direction of the conductor layer from a tip of the lower surface, the side surface has a contour having an inwardly recessed curve line and having a portion receding in the normal direction of the conductor layer from the tip of the upper surface, and a connection portion between the upper surface and the side surface has a rounded shape such that a maximum radius R of a circle is 0.1 μm≤R≤5 μm on average.