We report low-temperature conductance measurement on a Coulomb-blockaded do
t in a silicon-on-insulator-based single-electron transistor with in-plane
side gates. The linear conductance for 4.2 K at zero magnetic field exhibit
s up to three paired peaks, indicating simple alternating odd (spin 1/2)-ev
en(spin 0) filling. Three intrapair spacings are found to be nearly a const
ant value, corresponding to the single charging energy U, whereas two inter
pair spacings are different which are associated with U+Delta E-1 and U+Del
ta E-2, i.e., successive quantized level spacings added to U. The quantized
level spacings were also revealed in the nonlinear current staircases. (C)
2000 American Institute of Physics. [S0003-6951(00)05141-X].