  Based on a four-layered self-doped $t-J$ type model and the slave-boson
mean-field approach, we study theoretically the superconductivity in the
electron-doped and hole-doped layers. The neighbor layers are coupled through
both the single electron interlayer hopping and pair tunneling effect. The
superconducting gap magnitude for the electron-doped band is nearly twice of
that of the hole-doped one, which contrasts to our previous understanding of
the electron-hole asymmetry in high-T$_c$ superconductors but consistent with
recent angle-resolved-photoemission-spectroscopy experiments in four-layered
materials Ba$_2$Ca$_3$Cu$_4$O$_8$F$_2$. Our results propose that the pair
tunneling effect is important to examine the multi-layered superconducting
materials.
