Metal Insulator Semiconductor Research Articles

N-Polar GaN HEMTs in a High-Uniformity 100-mm Wafer Process With 43.6% Power-Added Efficiency and 2 W/mm at 94 GHz

We report the fabrication of N-polar GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) with a power-added efficiency (PAE) of 43.7% from an 8-V supply measured by load pull at 94 GHz. The devices are fabricated on 100-mm SiC substrates and exhibit excellent uniformity, constituting the first report on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$W$</tex-math> </inline-formula> -band power performance across a 100-mm N-polar GaN sample. Compared with the available efficiency of N-polar GaN on SiC at 94 GHz, the devices presented here demonstrate among the highest PAE performance, while delivering a power density of 2 W/mm, competitive with highly scaled, and previously reported both Ga and N-polar devices using an 8-V power supply.

"Blue-free" orange ZnO-related light-emitting diode based on a natural interface layer of Ga2O3 and ZnGa2O4.

To fabricate a ZnO-related light-emitting diode (LED) with zero emission at blue wavelengths ("blue-free"), an ingenious strategy is employed. Specifically, for the first time to the best of our knowledge, a natural oxide interface layer, possessing remarkable visible emission potential, is introduced into the Au/i-ZnO/n-GaN metal-insulator-semiconductor (MIS) structure. The unique Au/i-ZnO/interface layer/n-GaN structure successfully eliminated the harmful blue emissions (400-500 nm) from the ZnO film, and the remarkable orange electroluminescence is mainly attributed to the impact ionization process of the natural interface layer at high electric field. It is worth mentioning that the device achieved ultra-low color temperature (2101 K) and excellent color rendering index (92.8) under electrical injection, indicating that the device could fulfill the requirements of electronic display systems and general illumination, and might even play unexpected roles in special lighting domains. The results obtained provide a novel and effective strategy for the design and preparation of ZnO-related LEDs.

Acoustically Operated Excitonic Transistor Using Poly(3-hexylthiophene)

An organic semiconductor, regioregular poly(3-hexylthiophene) (rrP3HT), based excitonic transistor on a piezoelectric YZ lithium niobate substrate is reported for the first time. The propagating surface acoustic wave (SAW) field ionizes the excitons, stores the charge pair in the SAW modulated potential field in the semiconductor, and carries them forward. A long-range transport ∼4.7 mm at room temperature has been demonstrated. The electrical control of the exciton flux was achieved with SAW propagating through a dual metal–insulator–semiconductor (MIS) structure. The working of the device has been demonstrated using white and green light. A threshold voltage of −20.65 V was observed, and the working mechanism of the proposed device has been verified through numerical analysis using MATLAB. The potential use of the proposed device structure as an all optical device was verified electrically with additional electrode terminals at the output end.

Direct Vibrational Stark Shift Probe of Quasi-Fermi Level Alignment in Metal Nanoparticle Catalyst-Based Metal-Insulator-Semiconductor Junction Photoelectrodes.

Photoelectrodes consisting of metal-insulator-semiconductor (MIS) junctions are a promising candidate architecture for water splitting and for the CO2 reduction reaction (CO2RR). The photovoltage is an essential indicator of the driving force that a photoelectrode can provide for surface catalytic reactions. However, for MIS photoelectrodes that contain metal nanoparticles, direct photovoltage measurements at the metal sites under operational conditions remain challenging. Herein, we report a new in situ spectroscopic approach to probe the quasi-Fermi level of metal catalyst sites in heterogeneous MIS photoelectrodes via surface-enhanced Raman spectroscopy. Using a CO2RR photocathode, nanoporous p-type Si modified with Ag nanoparticles, as a prototype, we demonstrate a selective probe of the photovoltage of ∼0.59 V generated at the Si/SiOx/Ag junctions. Because it can directly probe the photovoltage of MIS heterogeneous junctions, this vibrational Stark probing approach paves the way for the thermodynamic evaluation of MIS photoelectrodes with varied architectural designs.

Effects of oxygen contents on the physical properties of MgO films and carrier transport of Au/MgO/ZnO MIS diodes

MgO films with various oxygen contents were deposited on ZnO using radio-frequency magnetron sputtering, and Au/MgO/ZnO metal-insulator-semiconductor (MIS) diodes were fabricated. The effects of various oxygen contents on the physical properties of MgO and the carrier transport in MIS diodes were studied. The crystallinity of MgO films improved with increased oxygen content up to 66%; however, the crystallinity degraded upon further increase of oxygen content up to 100%. X-ray photoelectron spectroscopy showed that the oxygen vacancies were compensated by the introduced oxygen atoms; however, the excess oxygen atoms could not fill the lattice sites and were instead absorbed on the MgO surface. The optical bandgaps of MgO films increased from 5.16 to 5.22 eV for 0 and 100% oxygen content, respectively, resulted by the suppressed oxygen vacancies. The average roughness of MgO films increased from 4.02 to 6.86 nm for 0 and 100% oxygen content, respectively. As compared to MIS diodes without oxygen content, the leakage current was reduced by approximately 300 times in MIS diodes with 66% oxygen content. At a high bias voltage (V ≥ 0.4V), MIS diodes without oxygen exhibited ohmic conduction. In contrast, MIS diodes with oxygen exhibited Fowler-Nordheim tunnelling at high bias voltages. With increasing oxygen content, the tunnelling barrier height increased to its maximum of 0.46 eV in MIS diodes with 66% oxygen content. Nevertheless, the barrier height reduced to 0.29 eV for the excess oxygen content up to 100%. However, at low-bias voltages, all MIS diodes demonstrated a direct tunnelling mechanism owing to their rectangular barriers.

Preparation of Remote Plasma Atomic Layer-Deposited HfO2 Thin Films with High Charge Trapping Densities and Their Application in Nonvolatile Memory Devices.

Optimization of equipment structure and process conditions is essential to obtain thin films with the required properties, such as film thickness, trapped charge density, leakage current, and memory characteristics, that ensure reliability of the corresponding device. In this study, we fabricated metal-insulator-semiconductor (MIS) structure capacitors using HfO2 thin films separately deposited by remote plasma (RP) atomic layer deposition (ALD) and direct-plasma (DP) ALD and determined the optimal process temperature by measuring the leakage current and breakdown strength as functions of process temperature. Additionally, we analyzed the effects of the plasma application method on the charge trapping properties of HfO2 thin films and properties of the interface between Si and HfO2. Subsequently, we synthesized charge-trapping memory (CTM) devices utilizing the deposited thin films as charge-trapping layers (CTLs) and evaluated their memory properties. The results indicated excellent memory window characteristics of the RP-HfO2 MIS capacitors compared to those of the DP-HfO2 MIS capacitors. Moreover, the memory characteristics of the RP-HfO2 CTM devices were outstanding as compared to those of the DP-HfO2 CTM devices. In conclusion, the methodology proposed herein can be useful for future implementations of multiple levels of charge-storage nonvolatile memories or synaptic devices that require many states.

Accurate determination of band tail properties in amorphous semiconductor thin film with Kelvin probe force microscopy

The disordered microscopic structure of amorphous semiconductors causes the formation of band tails in the density of states (DOS) that strongly affect charge transport properties. Such band tail properties are crucial for understanding and optimizing thin-film device performance with immense relevance for large area electronics. Among the available techniques to measure the DOS, Kelvin Probe Force Microscopy (KPFM) is exceptional as it enables precise local electronic investigations combined with microscopic imaging. However, a model to interpret KPFM spectroscopy data on amorphous semiconductors of finite thickness is lacking. To address this issue, we provide an analytical solution to the Poisson equation for a metal–insulator–semiconductor junction interacting with the atomic force microscope tip. The solution enables us to fit experimental data for semiconductors with finite thickness and to obtain DOS parameters, such as band tail width, doping density, and flat band potential. To demonstrate our method, we perform KPFM experiments on Indium–Gallium–Zinc Oxide (IGZO) thin-film transistors (IGZO-TFTs). DOS parameters compare well with values obtained with photocurrent spectroscopy. We demonstrate the relevance of the developed method by investigating the impact of ionizing radiation on DOS parameters and TFT performance. Our results provide clear evidence that the observed shift in threshold voltage is caused by static charge in the gate dielectric, leading to a shift in flat band potential. Band-tails and doping density are not affected by the radiation. The developed methodology can be easily translated to different semiconductor materials and paves the way for quantitative microscopic mapping of local DOS parameters in thin-film devices.

DC and RF performance of HR Si(111)-based AlGaN/GaN MIS-HEMT with a symmetrical multi-finger grid array structure for 5G N28 700MHz low-bias-control applications

HR Si(111)-based AlGaN/GaN metal insulator semiconductor high electron mobility transistor (MIS-HEMT) for 5G mobile communication at N28 700 MHz band is proposed in this paper. The device is ingeniously designed with a symmetrical dual-column multi-finger grid array structure. In addition, the device is designed with an MIS gate with a 6 nm SiN dielectric film to suppress the leakage current and a source field plate to suppress the current collapse effect. The fabrication process of the device is studied in detail, including the epitaxial surface treatment, F ion implantation isolation, ohmic contact, electron beam lithography gate process, surface passivation, and source field plate. A device with a gate length of 0.25 μm, gate-source space of 1 μm, a gate width of 1200 μm (the number of gate fingers is 12 with a single-finger gate width of 100 μm), and source field plate length of 0.2 μm is fabricated successfully. Results of electrical tests show that the HEMT device has a threshold voltage of about −7.5 V, a low knee voltage of about 4 V, a high saturation drain current density of 750 mA/mm, and a gate leakage current as low as less than 160 pA at the gate bias of 0 V. At the frequency band of 703–803 MHz, with low bias control of 10 V, the S21 of HEMT is about 5.923–7.261 dB, the gain flatness is 1.338 dB, the current gain is about 27.3 dB, and the stability factor is more than 1. This device would be a good candidate for future 5G low-frequency and low-voltage-control applications.

Paralleled multi-GaN MIS–HEMTs integrated cascode switch for power electronic applications

A cascode gallium nitride (GaN) switch integrating four paralleled GaN depletion-mode metal–insulator–semiconductor–high-electron-mobility transistors (MIS–HEMT) and a silicon MOSFET (Si-MOSFET) is presented. Each GaN chip is wire-bonded into a multi-chip power module to scale up the power rating. An optimized symmetric configuration and wire bonding of an integral package are used in the cascode switch. By utilizing an optimized packaging approach, the performance of the multi-GaN-chip cascode switch was evaluated through both static and dynamic characterizations. The constructed cascode switch provides a low-static on-state resistance of 72 mΩ and an off-state blocking capability of 400 V with a positive threshold voltage of 2 V. Analysis of dynamic switching characteristics are discussed and demonstrates stable dynamic on-state resistance (R DS-ON) in inductive load circuits with switching dependencies of voltage, frequency, time, and temperature. The extended defects from buffer caused a minimal decrease in dynamic and static R DS-ON with respect to hard switching conditions. However, there was no noticeable degradation in R DS-ON under harsh switching conditions. This study provides a complete analysis of the multi-GaN-chip cascode switch, including MIS–HEMT manufacturing, cascode packaging and static and dynamic characterizations.

Recent Progress of E‐mode Gallium Nitride Metal–Insulator–Semiconductor ‐High Electron Mobility Transistors with Hybrid Ferroelectric Charge Trap Gate (FEG‐HEMT) for Power Switching Applications

Aluminum gallium nitride/gallium nitride (AlGaN/GaN) heterostructure devices have proven to be highly effective for high‐frequency power amplifiers and power switching applications with improved performance compared to those made with traditional silicon technology and other advanced semiconductor technologies. The development of enhancement‐mode (E‐mode) AlGaN/GaN high electron mobility transistors (HEMTs) and metal–insulator–semiconductor HEMTs (MIS‐HEMTs) has been a focus in recent years due to their potential applications. Arising from the concept of a flash‐memory‐like hybrid ferroelectric charge storage structure, the high‐performance hybrid ferroelectric charge storage gate (FEG) GaN HEMT has gradually gained a great deal of attention due to the concept being a useful and versatile tool to realize E‐mode operations. This article attempts to review the latest progresses in this technology, including alternative improvements and device characteristics. Future challenges for the E‐mode FEG‐HEMT are also discussed.

Effective Suppression of Amorphous Ga2O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal-Insulator-Semiconductor Electronic Devices.

Gallium nitride (GaN) has been considered one of the most promising materials for the next-generation power and radio-frequency electronic devices, as they can operate at higher voltage, higher frequency, and higher temperature, compared with their silicon (Si) counterparts. However, the fresh GaN surface is susceptible to the natural oxidation composed of Ga2O3, Ga2O, and other intermediate oxidation states. Moreover, the oxidized GaN surface no longer features the distinct atomic step-terrace morphology, resulting in a degraded interface when gate or passivation dielectrics are deposited without appropriate pretreatment. It is responsible for the degraded performance of GaN-based devices such as current collapse and threshold voltage instability. In this study, the proposed high-temperature (500 °C) remote plasma pretreatments (RPPs) can play a significant role in addressing the issue of the deteriorated GaN surface exposed to air. Atomic step-terrace morphology was recovered after 500 °C-RPP due to the removal of oxides and suboxides. First-principles calculations verified that Ga2O at the GaN surface leads to interface states at ∼2.9 eV (EC-E ∼ 0.4 eV) in the bandgap, which is consistent with the increase of interface states at the EC-E range of 0.4-0.9 eV measured through constant-capacitance deep-level transient spectroscopy. Meanwhile, deep interface states and surface-related current collapse are well suppressed in GaN metal-insulator-semiconductor devices. These improved properties by 500 °C-RPP are generalizable to a broader range, including pre-gate and pre-passivation treatment, of which a decent surface/interface is desirable for high-performance GaN-based devices.

Realizing improved performance of metal-insulator-semiconductor diodes with high-k MgO/SiOx stack

With the development of metal-insulator-semiconductor (MIS) field-effect transistors, the thickness of silicon dioxide (SiO2) must be scaled down; however, it causes a large gate leakage current and a low on/off current ratio. Magnesium oxide (MgO) exhibits a dielectric constant as high as 11.2, which is about three times larger than that (3.9) of SiO2; thus the thickness of MgO can be three times greater than that of SiO2 and significantly reduces the gate leakage current. Nevertheless, a large lattice mismatch (22.5%) exists between MgO and Si materials. In the study, the MgO/SiOx stack dielectrics are employed to suppress the large lattice mismatch and improve the performance of MIS diodes. The MgO/SiOx stack largely reduces the oxygen vacancy of MgO from 75% to 52.3%; also the fixed oxide charge and interface trap charge density are drastically decreased from 1.3 × 1012 and 1.8 × 1013 to 8.2 × 1011 cm−2 and 7.8 × 1012 cm−2eV−1, respectively. Compared to the MIS diodes with a single MgO, the MgO/SiOx stack dielectrics suppress the gate leakage current by about two orders in MIS diodes; hence the rectification ratio is enhanced from 114 to 1032 at ±2V. Band-diagram shows that Fowler-Nordheim tunneling occurs at a high reverse-bias voltage, and the barrier height increases from 0.18 to 0.42 eV in the MIS diodes with single MgO and MgO/SiOx stack dielectrics, respectively. Nevertheless, the MIS diodes operate through a direct tunneling at low reverse-bias voltages.

Theory and Simulation of Metal–Insulator–Semiconductor (MIS) Photoelectrodes

A metal-insulator-semiconductor (MIS) structure is an attractive photoelectrode-catalyst architecture for promoting photoelectrochemical reactions, such as the formation of H2 by proton reduction. The metal catalyzes the generation of H2 using electrons generated by photon absorption and charge separation in the semiconductor. The insulator layer between the metal and the semiconductor protects the latter element from photo-corrosion and, also, significantly impacts the photovoltage at the metal surface. Understanding how the insulator layer determines the photovoltage and what properties lead to high photovoltages is critical to the development of MIS structures for solar-to-chemical energy conversion. Herein, we present a continuum model for charge-carrier transport from the semiconductor to the metal with an emphasis on mechanisms of charge transport across the insulator. The polarization curves and photovoltages predicted by this model for a Pt/HfO2/p-Si MIS structure at different HfO2 thicknesses agree well with experimentally measured data. The simulations reveal how insulator properties (i.e., thickness and band structure) affect band bending near the semiconductor/insulator interface and how tuning them can lead to operation closer to the maximally attainable photovoltage, the flat-band potential. This phenomenon is understood by considering the change in tunneling resistance with insulator properties. The model shows that the best MIS performance is attained with highly symmetric semiconductor/insulator band offsets (e.g., BeO, MgO, SiO2, HfO2, or ZrO2 deposited on Si) and a low to moderate insulator thickness (e.g., between 0.8 and 1.5 nm). Beyond 1.5 nm, the density of filled interfacial trap sites is high and significantly limits the photovoltage and the solar-to-chemical conversion rate. These conclusions are true for photocathodes and photoanodes. This understanding provides critical insight into the phenomena enhancing and limiting photoelectrode performance and how this phenomenon is influenced by insulator properties. The study gives guidance toward the development of next-generation insulators for MIS structures that achieve high performance.

A thorough study on the electrical performance change and trap evolution of AlGaN/GaN MIS-HEMTs under proton irradiation

In this work, the effects of proton-induced trap evolution on the electrical performances of AlGaN/GaN metal–insulator–semiconductor (MIS) high-electron-mobility-transistors (HEMTs) have been investigated in detail. Contrary to observed proton-induced degradation in sheet electron density (ns), carrier mobility (μn), and sheet resistance (RSH), a significant improvement in gate leakage current (IG) and off-state drain–source breakdown voltage (BVDS) is found in irradiated devices. The low-frequency noise (LFN) results show that the density of traps in the AlGaN layer and AlGaN/GaN interface increases after irradiation, which leads to a degradation in ns, μn, and RSH and an improvement in BVDS due to enhanced electron trapping and depletion. Furthermore, the measurement results obtained from the frequency-dependent conductance technique show that irradiated devices exhibit decreased trap density (DT) at the insulator/semiconductor interface with hardly changed trap energy level (ET), which confirms the observed proton-induced decrease in IG. An increase in DT at the AlGaN/GaN interface is also found after irradiation, which is consistent with LFN results. These traps with deeper ET induce a serious Coulomb scattering effect. This work provides valuable information for the systematic understanding of the proton irradiation effect of AlGaN/GaN MIS-HEMTs.

Trap‐Assisted Memristive Switching in HfO2‐Based Devices Studied by In Situ Soft and Hard X‐Ray Photoelectron Spectroscopy

AbstractMemristive devices are under intense development as non‐volatile memory elements for extending the computing capabilities of traditional silicon technology by enabling novel computing primitives. In this respect, interface‐based memristive devices are promising candidates to emulate synaptic functionalities in neuromorphic circuits aiming to replicate the information processing of nervous systems. A device composed of Nb/NbOx/Al2O3/HfO2/Au that shows promising features like analog switching, no electro‐forming, and high current‐voltage non‐linearity is reported. Synchrotron‐based X‐ray photoelectron spectroscopy and depth‐dependent hard X‐ray photoelectron spectroscopy are used to probe in situ different resistance states and thus the origin of memristive switching. Spectroscopic evidence for memristive switching based on the charge state of electron traps within HfO2 is found. Electron energy loss spectroscopy and transmission electron microscopy support the analysis. A device model is proposed that considers a two‐terminal metal–insulator–semiconductor structure in which traps within the insulator (HfO2/Al2O3) modulate the space charge region within the semiconductor (NbOx) and, thereby, the overall resistance. The experimental findings are in line with impedance spectroscopy data reported in the companion paper (Marquardt et al). Both works complement one another to derive a detailed device model, which helps to engineer device performance and integrate devices into silicon technology.

Pulsed laser deposited Dy and Ta doped hafnium- zirconium oxide thin films for the high-k applications

Hf0.6Zr0.2Dy0.1Ta0.1O2 thin films were deposited on Si (100) at 600°C using pulsed laser deposition for gate oxide applications because of the compatibility of the elements with the CMOS process. Special emphasis was placed on the properties of Hf0.6Zr0.2Dy0.1Ta0.1O2 thin films within metal-insulator-semiconductor (MIS) structure (Pt/Hf0.6Zr0.2Dy0.1Ta0.1O2/Si) for high-k application in logic devices. The capacitance-voltage and current-voltage measurements are used to determine the electrical characteristics of MIS capacitor structures. The minimum equivalent oxide thickness and maximum dielectric constant of the thin films obtained were as low as 1.2 nm and as high as 35.7 at 10 kHz, respectively. Results on the gate stacks obtained based on the MIS structures appear to be promising as the high-k material for logic devices.

Mn-Doped Ge Nanoparticles Grown on SiO2 Thin Films by Molecular Beam Epitaxy for Photodetector and Solar Cell Applications

In this work, we propose a novel efficient strategy based on the combination of molecular beam epitaxy deposition and the solid-state dewetting process for the growth and self-assembly of magnetic GeMn nanoparticles on the SiO2 substrate. Morphological and structural investigations of magnetic GeMn nanoparticles carried out by AFM and HR-TEM microcopies show that these nanoparticles are very dense (1012 cm–2), are homogeneous, and have a free-defect single-crystalline Ge-Mn phase. The investigations of the magnetic properties carried out by a superconducting quantum interference device (SQUID) reveal that our magnetic GeMn nanoparticles are ferromagnetic and have a Curie record temperature of 325 K. The electrical characterizations of these GeMn nanoparticles when they are inserted in the insulator layer of a metal–insulator–semiconductor Schottky diode show that the nanoparticles contribute to electrical transport and photo-generation of hole–electron pairs when illuminated by white light, resulting in a significant increase in photocurrent of the order of 10 times. This novel growth strategy, which is compatible with CMOS technology, represents a promising path toward the real incorporation of diluted magnetic GeMn nanostructures in photodetection and photovoltaic technologies.

High voltage GaN vertical FinFET with a compatible integrated fin diode for low reverse conduction loss

A high-voltage normally-off GaN vertical FinFET with a compatible integrated Fin Diode (FD-FinFET) is proposed to improve reverse conduction performance. The Fin channel combined with the ohmic contact source covering the Fin sidewalls forms the Metal-Insulator- Semiconductor (MIS) structure to control the conduction/blocking characteristics of the FD. In the reverse conduction (VDS < 0 V), the FD easily turns on by the narrowing depletion region of the MIS and thus significantly reduces the turn-on voltage (VRT). With the increasing VSD, electron accumulation layers are formed along the Fin sidewalls and thus greatly improve the reverse current capacity. In the forward conduction and blocking state (VDS > 0 V and VGS > or = 0 V), the threshold voltage (VTH) and breakdown voltage (BV) of the FD-FinFET are hardly influenced by the FD because the FD channel is pinched off by the depletion effect. Therefore, a low VRT and a high VTH can be obtained synchronously. Consequently, when the gate biased-voltage (VGS) varies from 0 V to −3 V, the FD-FinFET can keep a low VRT of 0.49 V, while the VRT of the Con. FinFET rises significantly from 1.11 V to 4.11 V. Besides, it exhibits a high BV of 1725 V. The proposed structure not only avoids the difficulty of p-type doping, but also provides a new design concept to obtain a low reverse conduction loss, maintaining high forward conduction and blocking performances.

Deep sub-60 mV/dec subthreshold swing independent of gate bias sweep direction in an in situ SiN/Al0.6Ga0.4N/GaN-on-Si metal-insulator high electron mobility transistor

In this Letter, we demonstrated deep sub-60 mV/dec subthreshold swings (SS) independent of gate bias sweep direction in GaN-based metal–insulator–semiconductor high electron mobility transistors (MISHEMTs) with an Al0.6Ga0.4N/GaN heterostructure and in situ SiN as gate dielectric and surface passivation. Average SS values of 22 and 29 mV/dec over 3–4 orders of drain current (ID) swing were measured during forward and reverse sweeps, respectively, in a 75-nm gate length (LG) device. Sub-60 mV/dec SS was also observed in the GaN MISHEMTs with longer LG up to 350 nm. The intrinsic physical mechanisms of deep sub-60 mV/dec SS were comprehensively studied. The observed negative differential resistance in the gate current, the kinks in the output ID-VD curve, and the capacitance spike in the depletion region of the C–V curves suggest that the capture and emission of electrons in the traps are the dominant physical mechanisms responsible for the small SS.

Low-frequency noise characteristics of indium–gallium–zinc oxide ferroelectric thin-film transistors with metal–ferroelectric–metal–insulator–semiconductor structure

We investigate the low-frequency noise characteristics of indium–gallium–zinc oxide ferroelectric thin-film transistors (FeTFTs) with a metal–ferroelectric–metal–insulator–semiconductor (MFMIS) structure. MFMIS FeTFTs are fabricated with different metal-to-FE area ratios (AM/AF's). It is revealed that the noise generation mechanism differs depending on the operation region [low and high drain current (ID) regions] and AM/AF. Excess noise in the low ID region is observed in the MFMIS FeTFTs with AM/AF's of 4 and 6 due to carrier mobility fluctuations. In the high ID region, the carrier number fluctuation generates the 1/f noise of the devices regardless of the AM/AF.