A dielectric film containing Zr—Sn—Ti—O formed by atomic layer deposition using a TiI₄ precursor and a method of fabricating such a dielectric film produce a reliable dielectric layer having an equivalent oxide thickness thinner than attainable using SiO₂. Depositing titanium and oxygen onto a substrate surface by atomic layer deposition using a TiI₄ precursor, depositing zirconium and oxygen onto a substrate surface by atomic layer deposition, and depositing tin and oxygen onto a substrate surface by atomic layer deposition form the Zr—Sn—Ti—O dielectric layer. Dielectric films containing Zr—Sn—Ti—O formed by atomic layer deposition using TiI₄ are thermodynamically stable such that the Zr—Sn—Ti—O will have minimal reactions with a silicon substrate or other structures during processing.