We theoretically investigate quantum fluctuation of charge between even and
odd states of a normal-superconducting-normal single-electron tunneling
transistor. It is shown that due to the superconducting gap, the charge
fluctuation in the Coulomb blockade regime for even state is larger than that
for odd state. We show that large energy correction in the former regime caused
by charge fluctuation can be explained by considering the charging energy
renormalization.Comment: 4 pages, 3 figures, prepared for Proccedings of International
Symposium on Superconducting Device Physics (SDP 2001