An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

Microstructural design of hard coatings

The recent progress in ferroelectricity and antiferroelectricity in HfO2-based thin films is reported. Most ferroelectric thin film research focuses on perovskite structure materials, such as Pb(Zr,Ti)O3, BaTiO3, and SrBi2Ta2O9, which are considered to be feasible candidate materials for non-volatile semiconductor memory devices. However, these conventional ferroelectrics suffer from various problems including poor Si-compatibility, environmental issues related to Pb, large physical thickness, low resistance to hydrogen, and small bandgap. In 2011, ferroelectricity in Si-doped HfO2 thin films was first reported. Various dopants, such as Si, Zr, Al, Y, Gd, Sr, and La can induce ferro-electricity or antiferroelectricity in thin HfO2 films. They have large remanent polarization of up to 45 μC cm(-2), and their coercive field (≈1-2 MV cm(-1)) is larger than conventional ferroelectric films by approximately one order of magnitude. Furthermore, they can be extremely thin ( 5 eV). These differences are believed to overcome the barriers of conventional ferroelectrics in memory applications, including ferroelectric field-effect-transistors and three-dimensional capacitors. Moreover, the coupling of electric and thermal properties of the antiferroelectric thin films is expected to be useful for various applications, including energy harvesting/storage, solid-state-cooling, and infrared sensors.

Ferroelectricity and Antiferroelectricity of Doped Thin HfO2‐Based Films

Exploring dynamics in the far-infrared with terahertz spectroscopy.

Thermal stability of nitride thin films

Thin films of multiferroic (Bi0.6Tb0.3La0.1)FeO3 were grown on Pt∕Ti∕SiO2∕Si substrate under various oxygen pressures by pulsed laser deposition technique. X-ray diffraction patterns show that the crystallinity of the thin film is improved with decreasing depositing oxygen pressure and the thin film grown at a lower oxygen pressure of 0.01torr exhibits a single perovskite phase with preferred (001) orientation. Leakage current of the as-deposited thin films decreases with decreasing grown oxygen pressure. Significantly, the leakage current of the thin films can be reduced largely by an annealing process at 800°C with flowing oxygen. The annealed thin films show a relatively high resistivity and stable polarization loops with double remnant polarization of about 3μC∕cm2. The conduction properties of the thin films have been well analyzed, and it is indicated that the dominant conduction mechanism is the space-charge-limited conduction for the thin film grown at higher oxygen pressure and the Poole-Frenkel ...

Leakage current of multiferroic (Bi0.6Tb0.3La0.1)FeO3 thin films grown at various oxygen pressures by pulsed laser deposition and annealing effect

High-field magnetization processes of S =1/2 double spin chain systems KCuCl 3 and TlCuCl 3 have been measured up to 39 T at 4.2 and 1.7 K for both systems and at 1.0 and 0.5 K for TlCuCl 3 using s...

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High-Field Magnetization Processes of Double Spin Chain Systems KCuCl 3 and TlCuCl 3

Self-aligned-gate Pt/SrBi2Ta2O9/HfAlO/Si metal/ferroelectric/insulator/semiconductor (MFIS) field-effect transistors (FETs) were fabricated. Drain current (Id) versus gate voltage curves of the MFIS FETs showed almost the same steepness as that of a non-self-aligned-gate Pt/HfAlO/Si metal/insulator/semiconductor FET. Long retention times with large on- and off-state Id ratios were obtained for the MFIS FETs. The retention times more than 33 days with an on- and off-state Id ratio over 105 were demonstrated for the self-aligned-gate MFIS FET with a 2-µm-long and 80-µm-wide gate. This device showed the longest memory retention among all of the ferroelectric-gate FETs reported ever before.

https://iopscience.iop.org/article/10.1143/JJAP.44.L800/pdf

Self-Aligned-Gate Metal/Ferroelectric/Insulator/Semiconductor Field-Effect Transistors with Long Memory Retention

High field magnetization and susceptibility measurements have been performed on an S=1 antiferromagnetic chain compound with bond alternation: [ Ni 2 ( Medpt ) 2 (μ− ox )(μ− N 3 )] ClO 4 ·0.5 H 2 O ( Medpt=methyl−bis (3− aminopropyl)amine ). When the magnetic field is applied along the chain direction, no magnetization is observed in the low field region. Then, the magnetization curve rises at about 17 T and increases almost linearly up to about 43 T to reach a plateau which corresponds to half of the saturated moment, and shows a steep increase again at about 55 T. The alternating ratio α is estimated to be ∼0.3 by comparing the experimental results with the calculations for the magnetization and susceptibility. Accordingly, the ground state of this compound is in the singlet-dimer phase.

High field magnetization in an S=1 antiferromagnetic chain with bond alternation

We have investigated ferroelectric-gate field-effect transistors (FeFETs) with Pt/SrBi2Ta2O9/(HfO2)x(Al2O3)1−x (Hf-Al-O) and Pt/SrBi2Ta2O9/HfO2 gate stacks. The fabricated FeFETs have excellent data retention characteristics: The drain current ratio between the on- and off-states of a FeFET was more than 2 × 106 after 12 days, and the decreasing rate of this ratio was so small that the extrapolated drain current ratio after 10 years is larger than 1 × 105. A fabricated self-aligned gate Pt/SrBi2Ta2O9/Hf-Al-O/Si FET revealed a sufficiently large drain current ratio of 2.4 × 105 after 33.5 day, which is 6.5 × 104 after 10 years by extrapolation. The developed FeFETs also revealed stable retention characteristics at an elevated temperature up to 120 °C and had small transistor threshold voltage (Vth) distribution. The Vth can be adjusted by controlling channel impurity densities for both n-channel and p-channel FeFETs. These performances are now suitable to integrated circuit application with nonvolatile functions. Fundamental properties for the applications to ferroelectric-CMOS nonvolatile logic-circuits and to ferroelectric-NAND flash memories are demonstrated.

https://www.mdpi.com/1996-1944/3/11/4950/pdf

Mitsue Takahashi

Papers

Leakage current of multiferroic (Bi0.6Tb0.3La0.1)FeO3 thin films grown at various oxygen pressures by pulsed laser deposition and annealing effect

High-Field Magnetization Processes of Double Spin Chain Systems KCuCl 3 and TlCuCl 3

Self-Aligned-Gate Metal/Ferroelectric/Insulator/Semiconductor Field-Effect Transistors with Long Memory Retention

High field magnetization in an S=1 antiferromagnetic chain with bond alternation

Recent Progress of Ferroelectric-Gate Field-Effect Transistors and Applications to Nonvolatile Logic and FeNAND Flash Memory.