A manufacturing method including supplying a first substrate including a first face designated front face, the front face being made of a III-V type semiconductor, supplying a second substrate, forming a radical oxide layer on the front face of the first substrate by executing a radical oxidation, assembling, by a step of direct bonding, the first substrate and the second substrate so as to form an assembly including the radical oxide layer intercalated between the first and second substrates, executing a heat treatment intended to reinforce the assembly interface, and making disappear, at least partially, the radical oxide layer.