Drain Induced Barrier Lowering (DIBL) was analyzed when the channel of Gate-All-Around (GAA) FET, which is the most promising in the miniaturizing transistor structure, has an elliptic cross-section. The oxide film structure used a stacked Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS) structure using SiO₂ and ferroelectric. An analytical DIBL model was presented to analyze the DIBL in elliptic GAA FET with ferroelectric. Its validity was proven by comparing the results of other papers. As a result, the Drain Induced Barrier Rising (DIBR) effect, that is, the negative DIBL effect, appeared depending on the ferroelectric thickness tfe, and the ratio of the remanent polarization Pr and coercive field Ec in the ferroelectric, Pr/Ec. The DIBL varied linearly with tfeEc/Pr, and the slope depended on the rate of change for the drain voltage of the ferroelectric charge Q, dQ/dVds. The tfeEc/Pr value satisfying DIBL=0 mV/V decreased as eccentricity increased. The ferroelectric thickness tfe will have to be decreased because the subthreshold swing increases if the Pr/Ec is increased to reduce the tfeEc/Pr value. The threshold voltage increased at this time, but the effect was minimal.

This paper presented an analytical SS model to determine the subthreshold swing (SS) of an elliptic junctionless Gate- All-Around (GAA) FET using ferroelectric. Analyzing a GAA FET with an elliptic cross-section was essential because it is difficult to manufacture a perfectly circular GAA FET. The results of the proposed SS model agreed well with 2D numerical simulation. Using this analytical SS model, SS was analyzed for the eccentricity and the ratio (P_r/E_c) of permanent polarization P_r and coercive electric field E_c in an elliptic junctionless GAA FET with an MFMIS (Metal-Ferroelectric-Metal-Isulator- Semiconductor) structure using ferroelectric. As a result, the changing rate of the average surface potential due to the gate voltage increased and SS decreased as the eccentricity increased. It was found that the inner gate voltage amplified more than the outer gate voltage due to the ferroelectricity, better controlling the carriers in the channel, thereby reducing SS. As the P_r/E_c decreased, the changing rate of the ferroelectric charge for the outer gate voltage increased and SS decreased. As the eccentricity increased, the changing rate of SS for P_r/E_c decreased. There was no significant change in SS until the eccentricity was about 0.5. The SS began to decline above 0.5 due to the changes in ferroelectric charge, inner gate voltage, and average surface potential for the outer gate voltage.

A newly proposed T-shape piezoelectric actuator, composed of piezoelectric benders, was designed and studied. This actuator has four legs, and can walk in both forward and backward directions. The piezoelectric actuator has a simple structure and can be easily fabricated. It consists of a piezoelectric bender and a joint. The piezoelectric bender is composed of carbon and ceramic materials. Therefore, there is an advantage in that it can be fabricated on a very small scale. Elliptical displacements of the piezoelectric actuators were analyzed by finite element analysis. Elliptical motion at the tip occurred at two voltages having a 90-degree phase difference. Based on the finite element analysis results, prototype actuators with maximum displacements were fabricated, and the characteristics of their movements were characterized.

A functionally graded material (FGM) spacer, which the distribution of dielectric permittivity inside an insulator changes spatially, can considerably reduce the electric field concentration around a high-voltage electrode and along the gas-insulator interface when compared to a conventional spacer with a uniform permittivity distribution, In this research, we propose the FGM spacer with an elliptical permittivity distribution instead of that with a distribution of dielectric permittivity varying along a radial direction only in order to improve efficiently the insulation capability. The optimal design of the elliptical FGM spacer configuration is performed by using the response surface methodology (RSM) combined with the steepest descent method (SDM).

A novel design of a simple square-frame USM (ultrasonic motor) was proposed. The stator of the motor consists of a square-frame shape elastic body and four rectangular plate ceramics. The four ceramics were attached to inner surfaces of the square frame elastic body. The same phase voltages were applied to the ceramics on horizontal surfaces, and 90 degree phase difference voltage were applied to the ceramics on vertical surfaces. To find a model that generates elliptical motion at outside of the stator, the finite element analysis program ATILA was used. The analyzed results were compared to the experimental results. As result, the model EL10EH3ET0.5CL4 which generates the maximum elliptical displacement was chosen by analyzing the resonance mode according to changes in frequency.