High permittivity dielectrics and suitable substrates are studies intensively in the view of their use in VLSI design. A novel mixed high-k gate dielectric material, i.e., zirconium-doped tantalum oxide (Zr-doped TaOx) and Hafnium-doped tantalum oxide (Hf-doped TaOx) has been thoroughly studied for future MOSFET applications. Deposition of new high-k gate dielectric by mixing of Ta2O5 with ZrO2 and HfO2 using co-sputtering technique, to reach the requirements of thermodynamic stability, high range of amorphous-to-crystalline transition temperature, a large electrical band gap, and a large energy band barrier with Si for ULSI era. Extensive studies on the fabrication process and device characteristics have been accomplished. Hence this book is useful for the readers to know some significant issue on mixed high-k gate dielectric materials for high frequency devices.