A structure of a thermoelectric module including at least one substrate, a thermoelectric device and an insulation protection structure is provided. The thermoelectric device is disposed on the substrate. The insulation protection structure surrounds the thermoelectric device. The thermoelectric device includes at least three electrode plates, first type and second type thermoelectric materials and a diffusion barrier structure. First and second electrode plates among the three electrode plates are disposed on the substrate. The first type thermoelectric material is disposed on the first electrode plate. The second type thermoelectric material is disposed on the second electrode plate. A third electrode plate among the three electrode plates is disposed on the first type and second type thermoelectric materials. The diffusion barrier structure is disposed on two terminals of each of the first type and second type thermoelectric materials. A fabrication method of the foregoing thermoelectric module is also provided.