Ultra-thin Ti and Er co-doped HfO2 films were grown on Si substrate by RF sputtering at different compositions and subjected to rapid thermal annealing at 500 °C and 700 °C in nitrogen ambient for 60 s. Dielectric properties of ultrathin co doped with Tritium and Erbium into hafnium oxide (HfO2) with rapid thermal annealing (RTA) have been investigated. Ti and Er different contents doped HfO2 thin films about (5 to 10) nm thicknesses have been employed for Au/HfTiErO/Si/Au metal oxide semiconductor (MOS) structures fabrication. The fabricated MOS (Au/HfTiErO/Si/Au) structure has been used for extracting electrical properties such that, dielectric constant, effective charge carriers, flat band voltage, interface trap density and doping concentration through capacitance voltage measurements. The films compared at different contents used for Ti and Er doped with HfO2 on growth parameters, which could not showed excellent properties due to small thickness and other several defects during the depositions. While, the film annealed at 500 °C has the improved microstructure and electrical characteristics. Furthermore Atomic force microscopy and X-ray photo electron microscopy analysis verified the microstructure of HfTiErO gate oxide for future MOS devices.