We investigate the electronic state of the I I band d-p model on the two-dimensional triangular lattice simulating a CoO2 plane in the layered cobalt oxides such as NaxCoO2 and NaxCoO2 center dot yH(2)O. The tight-binding parameters are determined so as to fit the LDA band structure. Using the slave boson approach together with the 1/N expansion method, we obtain the renormalized quasiparticle bands, where the a(1g) band with a large hole Fermi surface is largely renormalized due to the strong correlation effect, while the e'(g) bands with six hole pockets are almost unchanged. We also discuss the metal-insulator transition (MIT) with varying the d-p charge transfer energy Delta, and find that the MIT takes place at a critical value Delta(c) = 4.01 eV. (c) 2007 Elsevier B.V. All rights reserved.