We have developed a very controllable fabrication process of an extremely narrow (∼10 nm) quantum wire metal-oxide-semiconductor field-effect transistor (MOSFET) on a separation-by-implanted-oxygen (SIMOX) substrate using anisotropic etching and selective oxidation technique. The drain current versus gate voltage characteristics show oscillations caused by Coulomb blockade even at room temperature. The oscillations split into several sharp peaks when the temperature is decreased, indicating that the channel is separated by several serial coupled quantum dots and that the quantum levels of these dots correspond to the observed fine peaks.

We have fabricated and demonstrated ultrathin In-Ga-Zn-O (IGZO) channel ferroelectric HfO2 field effect transistor (FET) with memory operation. Ultrathin-body IGZO ferroelectric FET (FeFET) shows high mobility and nearly ideal subthreshold slop with minimum 8 nm channel thickness, thanks to the properties of IGZO material, junctionless FET operation, nearly-zero low-k interfacial layer on metal-oxide channel and effective capping for realizing ferroelectric phase formation with HfZrO2 (HZO). The controllable memory operations are achieved with the use of back gate. The design guideline of IGZO FeFET is proposed by discussing the thickness of front gate oxide HZO and back gate oxide SiO2 using TCAD simulation. The material and electrical properties of metal/HZO/IGZO/metal capacitor are also investigated. Metal/HZO/IGZO/metal capacitor has up to 10 8 endurance and over one-year retention. IGZO FeFET shows a potential for high-density and low-power memory application.

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We have investigated device design of HfO 2 -based ferroelectric tunnel junction (FTJ) memory. Asymmetry of dielectric screening property in top and bottom electrodes is the key for high tunneling electroresistance (TER) ratio. Thus, metal and semiconductor electrodes are proposed. There exists a design space of ferroelectric material parameters to achieve high TER ratio under the constraint of depolarizing field. We have developed an FTJ fabrication process to realize the design. Large polarization charge and symmetric switching voltage are obtained by top metal replacement process. High TER ratio >30 and multi-level cell operation have been successfully demonstrated. Retention characteristics is promising, however, endurance characteristics should be improved for reliable operation.INDEX TERMS Ferroelectric tunnel junction (FTJ), ferroelectric HfO 2 , tunneling electroresistance.