Nanostructures composed of Ag clusters on an Sb-terminated Si surface were designed in a highly controlled manner and the electric conduction through Ag nanoclusters to the silicon substrate was investigated by using a scanning tunneling microscopy/spectroscopy. It was found that the lateral conduction between neighboring Ag clusters significantly contributed to the tunneling current-voltage characteristics, and the metallic single-electron tunneling structures employing the lateral conduction channels at room temperature can be fabricated via a field-induced manipulation of Ag clusters. (C) 1999 American Institute of Physics. [S0003-6951(99)04627-6].