AbstractThis paper presents the comparison of the structural and electrical characteristics of Si/Si bonded interfaces depending on whether the surface layers were rendered amorphous by high dose ion implantation prior to annealing or not. While the general structure of the interfaces is the same when the wafers are preamorphized more precipitates are seen in the interface along with a few extended defects propagating into the volume. The most striking difference between both procedures is that the Spreading Resistance profile is more complicated in shape and difficult to master in the case of preamorphized wafers. Careful TEM analysis shows that only in this case the interfacial region is stressed in contrast with the fully relaxed structure obtained by direct bonding of crystalline wafers.For these reasons, there is little chance that the preamorphization technique will benefit to the bonding procedure of direct Si wafers.