We discuss processes for the fabrication of devices for thermoelectric generation, based on silicon nanostructures. The main issue that we address is the design and development of fabrication processes for devices exploiting a large number of interconnected nanostructures. Such devices are characterized by good mechanical strength and at the same time they can handle large currents and deliver high power. First, techniques based on lithography and conventional CMOS processing are presented. These techniques allow the fabrication of suspended silicon masses, connected with the silicon substrate through nanomembranes. Then, a low-cost process for the fabrication of forests of long silicon nanowires is presented. Finally, a technique for the fabrication of a contact at the top of this silicon nanowire forest is reported and discussed.