Mixed HfTaOx dielectric has been deposited by radio frequency (RF) magnetron co-sputtering of HfO2 and Ta2O5 targets on Si substrates and with Pt bottom electrode for metal–oxide–semiconductor (MOS) and metal–insulator–metal (MIM) structures, respectively. HfTaOx layers are characterized by X-ray photoelectron spectroscopy (XPS) to examine the chemical composition. Surface morphology and crystallinity of the deposited film were examined, using by atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXRD), respectively. For both the structures electrical properties have been studied in detail. MOS capacitor capacitance–voltage (C–V) characteristics have been utilized to determine the interface trap density and trap distribution in the silicon band gap. A small capacitance non-linearity and low dissipation factor were found in the Pt/HfTaOx/Pt MIM structures.