Quantum Cellular Automaton (QCA), which is one of the candidates for future integrable electron devices, is investigated from the viewpoint of operation temperature. The extended Hubbard model which can extract the physical essence of QCA is used to analyze the inter-cell interaction for a layered cell structure. We found that the operation energy estimated from the energy gap between the ground state and excited states of the layered structure is large enough to allow room temperature operation even if the size of quantum dot is as large as 500. The layered cell structure is found to be suitable for a memory application.

Fabrication methods of novel silicon quantum wires and dots using anisotropic wet chemical etching and thermal oxidation are newly proposed. The method realizes fine Si quantum wires, which are fully surrounded by the thermal SiO2 without any defects. The wires are straight and the Si/SiO2 interfaces are fairly flat. The 10 nm width wires are confirmed by Transmitting Scanning Microscopy observation in minimum size. The fine quantum dots are also fabricated using this method. The characteristics of the wires are investigated and the current oscillations in variation with the gate voltage are observed in low temperature. We believe the origin of these oscillations arise from one-dimensional subband conduction.