The present description concerns a process including the following steps: providing a plurality of assemblies, each including a donor substrate covered by a functional block successively including a first interconnection layer, a functional layer, and a second interconnection layer, the functional layer including one or more electronic components, the interconnection layers including a dielectric material in which are formed conductive elements, a first surface of the first interconnection layer in contact with the donor substrate and the free surface of the second interconnection layer being planarized so as to be compatible with a subsequent direct bonding, successively transferring, onto a receiver substrate the functional blocks, by direct bonding, to form a 3D assembly comprising a receiver substrate covered by a stack of two functional blocks.