The strong reduction of thermal conductivity with respect to bulk siliconThe strong reduction of thermal conductivity with respect to bulk siliconmakes nanostructured silicon one of the best materials for highly efficientdirect conversion of heat into electrical power and vice-versa. The widespreadtechnologies for the integration of silicon devices can be used to defineon-chip micro thermoelectric generators (scavengers); similar structures couldalso be used for precise and well-localized cooling through the reverse processof heat pumping. However, the road to the fabrication of integrated thermalenergy scavengers or cooler, based on silicon, is still very long. In this work,the design and the fabrication process of on-chip thermoelectric devices basedon a large number of interconnected monocrystalline silicon nanobeams,very tall (>1 μm) and thin (less than 200 nanometers), arranged in large areascombs is shown. The small width of the nanobeams gives a reduced thermalconductivity, and the height perpendicular to the substrate allows the definitionof a highly dense collection of nanostructures. The total cross-section isfar broader than that of other nanostructures, a characteristic that guaranteesboth mechanical stability and larger deliverable power per unit area.