Toyohiro Chikyow

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We have clarified that, in a metal/high-k gate stack, as well as the variability introduced by random dopant fluctuations (RDF), the threshold voltage variability (TVV) is attributable to the crystal structure and grain size in the metal gate. We have successfully eliminated this additional factor by reducing the grain size in the metal gate. We(More)
The microscopic mechanism of the degradation occurring in HfO/sub 2/-based high-k/IL dual layer gate insulator has been investigated. The hole-injection-induced release of hydrogen from Si-H terminations causes IL-breakdown. This mechanism accelerates NBTI. Defects due to electron-trapped oxygen vacancies are the origin of trap-assisted tunneling, causing(More)
Epitaxial synthesis and properties of novel Co and Mn-doped Ge magnetic semiconductors were studied. Epitaxial growth of high quality films with high doping concentrations has been stabilized by the use of two dopants. The magnetic and transport properties of the system exhibit high T(C) and large magnetoresistance effects that can be controlled(More)
Dilute magnetic semiconductors and wide gap oxide semiconductors are appealing materials for magnetooptical devices. From a combinatorial screening approach looking at the solid solubility of transition metals in titanium dioxides and of their magnetic properties, we report on the observation of transparent ferromagnetism in cobalt-doped anatase thin films(More)
Effects of nitrogen incorporation on suppression of electron charge traps in Hf-based high- kappa gate dielectrics have been studied by first-principles calculations, focusing on interactions between N atoms and electrons trapped at oxygen vacancies (V<sub>O</sub>'s). Our total energy calculations revealed that the formation energy of a doubly occupied(More)
Anomalous threshold voltage increase with area scaling of Mg- or La-incorporated high-k gate dielectrics has great impact on scaled devices. This paper reveals that much amount of Mg or La capping effects for V<inf>t</inf> reduction was disappeared with the increase of electron mobility in narrow channel nMISFETs. This phenomenon is explained with(More)
Ferromagnetic semiconductors are believed to be suitable for future spintronics, because both charge and spin degrees of freedom can be manipulated by external stimuli. One of the most important characteristics of ferromagnetic semiconductors is the anomalous Hall effect. This is because the ferromagnetically spin-polarized carrier can be probed and(More)
We have constructed a universal theory of workfunctions at metal/Hf-based dielectrics interfaces by combining an oxygen vacancy effects and a new concept of generalized charge neutrality level. Our theory systematically reproduces the experimentally observed workfunctions of various gate materials, including the unusual behaviors of workfunctions of both(More)
A novel technique for the control of nitrogen (N) and oxygen (O) concentrations in the metal/high-k gate stacks is proposed. By inserting a reactive metal (Ti) layer remote from work function metal and high-k insulator, N and O concentration is easily decreased. This technique effectively suppresses the EOT increase after high-temperature annealing.(More)