Uniformly doped Si single-electron transistors consisting of a one-dimensional regular array of multiple tunnel junctions (MTJs) and islands have been fabricated. The Coulomb blockade effect is found to play an important role in carrier conduction in the MTJ system at low temperatures (6 K). The conduction mechanism can be interpreted well by considering soliton. The soliton extends less than three islands in our MTJs, and the energy of a single soliton is found to be 0.024 eV from an analysis of low-temperature current–voltage characteristics. For high-temperature operation, it is effective to reduce the parasitic capacitance of each island, which leads to an increase in soliton length.