A SOG(spin glass) solution with excellent wetting to Si wafers was prepared by acid-hydrolysis of Si(OEt)4 and Me2Si(OEt)2. The solution was spin coated on Si wafers, and effects of heat treatment of the film were characterized by TG/DTA, FTIR and Ellipsometry. Silica film was obtained by heat treatment at $600^{circ}C$ within one hour, but heat treatment at 80$0^{circ}C$ caused interfacial oxidation of the silicon substrate. Unexpectedly silica films with much better adhesion were obtained by curing at $600^{circ}C$ for over 30 min. than those obtained by thermal oxidation.