The process for manufacturing a through insulated interconnection is performed by forming, in a body of semiconductor material, a trench extending from the front (of the body for a thickness portion thereof; filling the trench with dielectric material; thinning the body starting from the rear until the trench, so as to form an insulated region surrounded by dielectric material; and forming a conductive region extending inside said insulated region between the front and the rear of the body and having a higher conductivity than the first body. The conductive region includes a metal region extending in an opening formed inside the insulated region or of a heavily doped semiconductor region, made prior to filling of the trench.