Intermetallic dielectric layer was formed by using SiO$_2$/SOG/SiO$_2$ for aluminum based dual-metal interconnection process and its electric characteristics were evaluated. The dielectric layer was in the cost and facility point of view more useful than the insulator that was formed by etch-back process. The planarity by using SOG process was about 40% higher than that of the insulator by the CVD process. When SiO$_2$ films were deposited by the PECVD process the Al hillock formation during the next process was restrained bucause the intermetalic insulator was made at low temperature. The leakage current was 1${ imes}10^{7}~1{ imes}10^{-8}A/cm^{2}$ at the electric field of 10$^{5}$V/cm and breakdown filed was 4.5${ imes}10^{6}~7{ imes}10^{6}A/cm$. So we had confirmed that siloxane SOG was very useful for intermetallic layer material.