The use of atomic layer deposition (ALD) to form an amorphous dielectric layer of titanium oxide (TiO.sub.x) doped with lanthanide elements, such as samarium, europium, gadolinium, holmium, erbium and thulium, produces a reliable structure for use in a variety of electronic devices. The dielectric structure is formed by depositing titanium oxide by atomic layer deposition onto a substrate surface using precursor chemicals, followed by depositing a layer of a lanthanide dopant, and repeating to form a sequentially deposited interleaved structure. Such a dielectric layer may be used as the gate insulator of a MOSFET, as a capacitor dielectric, or as a tunnel gate insulator in flash memories, because the high dielectric constant (high-k) of the film provides the functionality of a thinner silicon dioxide film, and because the reduced leakage current of the dielectric layer when the percentage of the lanthanide element doping is optimized.