Fumiyoshi Yoshioka

Study of an Elevated Drain Fabrication Method for Ultra-Shallow Junction

An elevated diffusion layer fabricated from polycrystalline silicon (poly-Si) by solid phase diffusion was investigated in detail by secondary-ion mass spectroscopy (SIMS) analysis. We clarified that it was necessary to control the native oxide in the poly-Si/Si substrate interface and use small-grained poly-Si to fabricate uniform and controllable shallow junctions. The low-capacitance sidewall-elevated drain (LCSED) metal oxide semiconductor field-effect transistor (MOSFET) fabricated by the oxygen-free load-lock low-pressure chemical vapor deposition (LPCVD) poly-Si (L/L poly-Si) was extremely effective for marked scaling down of transistor size and realizing an ultra low reversed junction leakage current.

Control Of Single-Electron Device Using Environmental Impedance Modulation

A single-electron-tunneling (SET) device with variable environmental impedance is investigated. A self-consistent numerical calculation shows that the resistive environmental impedance can control the SET device. It is experimentally observed that the Coulomb gap becomes wider as the resistive environmental impedance becomes larger as predicted by the calculation. From discussion of the shape of the Coulomb diamond, it is concluded that the observed enlargement of the Coulomb gap is due to the electromagnetic environment effect of the Coulomb blockade.

Single-Electron Tunnelling Device with Variable Environmental Impedance

A single-electron tunnelling (SET) device consisting of a double junction and an environmental impedance is considered. Current-voltage characteristics are calculated using a self-consistent treatment of the environmental impedance. It is observed experimentally that Coulomb gaps become wide for large environmental resistances, which is in agreement with the theory. This modulation of the Coulomb gap by the environmental resistance can be a new operation principle of SET devices.