**1. Introduction**

Tiny electrical components are now unanimously required to be high in functionality and reliability and low priced in response to progress in the high density mounting technology.

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Continued device scaling for future technology nodes requires reduction in equivalent oxide thickness (EOT) of gate dielectrics to maintain electrostatic control of the charges induced in the channel. The use of amorphous SiO2 as a gate dielectric offers several key advantages in complementary metal-oxide semiconductor (CMOS) processing, including thermal and chemical stability as well as superior electrical isolation properties (high band gap of nearly 9 eV, and a Si–SiO2 potential barrier for electrons of about 3 eV). The continuous miniaturization of Si electronics has imposed severe constraints on the performance of the SiO2 gate oxide, with its thickness now approaching the quantum tunneling limit [1,2]. To continue the downward scaling, dielectrics with a higher dielectric constant (high-*k*) are being suggested as a solution to achieve the same transistor performance while maintaining a relatively thick physical thickness. Following this roadway, many materials systems (viz. lead–free non-ferroelectric) are currently under consideration as alternatives to conventional silicon oxide films as the gate dielectric material for sub-0.1 μm CMOS technology. Such an approach allows one to employ the best available materials for each phase, whose properties are known a priority due to the scarcity of high-*k* materials, to suit the desired application. Recent reports of giant dielectric constant have directed considerable attention to several new material systems, such as perovskite–related materials ACu3Ti4O12 (A = Ca, Bi2/3, Y2/3, La2/3) [3,4], La2/3Li*x*Ti1-*x*Al*x*O3 [5], Nd2O3 doped (1-*x*)Bi0.5Na0.5TiO3-*x*Bi0.5K0.5TiO3 [6], Fe-containing complex perovskites A(Fe1/2B1/2)O3 (A = Ba, Sr, Ca; B = Nb, Ta, Sb) [7,8], non-perovskite material Li0.05Ti0.02Ni0.93O [9], percolative BaTiO3-Ni composites [10], electron-doped manganites Ca1-*x*La*x*MnO3 and holedoped insulators La2Cu1-*x*Li*x*O4 and La2-*x*Sr*x*NiO4 [11–13]. The sensitivity of these complex oxides to strain, stoichiometry, phase heterogeneities, oxidation state, disorder, etc. can lead to drastic modifications in their magnetic and electric properties at the nanoscale. Besides that, as the key guidelines for replacing alternative dielectrics with high-*k* materials are required to (i) remain thermodynamically and chemically stable between the metal-oxide and Si substrate; (ii) kinetic stability against Si and the metal gate, in particular during high temperature processing and annealing; (iii) insulating properties: band offsets with Si over 1 eV to assure low leakage currents; (iv) a passivated, low-defect-density interface with Si to ensure large carrier mobility in the Si channel and good breakdown properties; and (v) interface quality between the high-*k* dielectrics and Si substrate: a low defect density in the high-*k* dielectric itself to prevent flat band and threshold voltage shifts and instabilities. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. The ranking of HfO2-based system as a desired high-*k* gate dielectric material to replace amorphous SiO2 drops considerably, as HfO2 suffers crystallization at a relatively low process temperature (< 500°C), resulting high leakage current along the grain boundaries [14]. Therefore, the exploitation of new type of amorphous phase pure high-*k* gate dielectrics candidates as a replacement of SiO2 still faces several daunting challenges.

Besides the aforementioned consideration, the superior electrical characteristics of the Si– SiO2 interface in ideal gate dielectric stack compatible with planarization technology has not achieved with any other alternative semiconductor–dielectric combination. Despite several key advantages of SiO2, the continual scaling of CMOS technologies has pushed the Si–SiO2 system in formidable challenge. One promising alternative approach to overcome the scaling limit has been proposed to substitute by silica-based single-valence nanoparticles (NPs) as gate insulator (interface between silicon and NP-oxides embedded silica), where flexibility, compartibility and functionality may be achieved through different NPs sizes/concentrations. Concentrating on the desired NP-oxides, potentially stable rare earth oxides (RE2O3, RE ~ rare earth, a series of elements from La to Lu with stable RE3+) were chosen, which are attractive materials based on good thermodynamic energy considerations with silicon, highly resistive and a high conduction band offset over 2 eV. We have presented extensive results, providing useful insight into the physics of nano-composite high-*k* gate dielectrics. Sol–gel derived nonmagnetic SiO2 glass matrix with magnetic/nonmagnetic rare earth NP-oxides provides a convenient way to tailor desired magnetic, dielectric (in presence of applied magnetic field), and other properties by altering the type, size and concentration of the dopant ions.
