Vulcanized tube having at least one foamed layer of elastomer material with a cellular structure with an average cell size in a range between 5 and 200 microns and the number of cells per unit of volume in a range between 1.9×105 and 1.4×109 cells/cm3. To form the tube, a forming device is inserted into an unvulcanized tube obtained in a prior initial stage of extrusion. At least one foaming agent is added to the elastomer material of the foamed layer in the initial stage of extrusion, such that the tube is vulcanized and the foamed layer is also simultaneously foamed. The vulcanizing process is carried out under pressure. Finally, in a stage of removal, the already vulcanized and foamed tube is removed from the forming device.