  We theoretically investigate the doping evolution of the electronic state of
high-Tc cuprate on both sides of the half-filling on the basis of the
three-dimensional three-band Hubbard model with a layered structure using the
Hartree-Fock approximation. Once a small amount of holes or electrons are doped
into the half-filled state, our model exhibits the charge-transfer
insulator-to-metal transition along with a chemical potential jump. At the same
time, the doped holes or electrons are inhomogeneously distributed, and they
tend to form clusters in the vicinity of the half-filling. This suggests the
possibility of microscopic phase separation with the separation between the
metallic and the insulating regions.
