The quantum mechanical effects in silicon single-electron transistors have been investigated. The devices have been fabricated in the form of point contact metal–oxide–semiconductor field-effect transistors with various channel widths using electron beam lithography and the anisotropic etching technique on silicon-on-insulator substrates. The device with an extremely narrow channel shows Coulomb blockade oscillations at room temperature. At low temperatures, negative differential conductances and fine structures are superposed on the device characteristics, which are attributed to the quantum mechanical effects in the silicon quantum dot in the channel. The energy spectrum of the dot is extracted from the experimental results. ©1997 American Institute of Physics.