Several recent experiments have revealed that the charge density \rho in a given compound (mostly underdoped) is intrinsic inhomogeneous with large spatial variations. Therefore, it is appropriate to define a local charge density \rho (r). These differences in the local charge concentration yield insulator and metallic regions, either in an intrinsic granular or in a stripe morphology. In the metallic region, the inhomogeneous charge density produces spatial or local distributions of superconducting critical temperatures T_c(r) and zero temperature gap \Delta ₀(r). We propose that the superconducting phase in high T_c oxides is reached when the temperature reach a value which superconduction regions with different critical temperatures percolates. We show also that this novel approach is able to reproduce the phase diagram for a family of cuprates and provides new insights on several experimental features of high T_c oxides.

PACS numbers: 74.72.--h, 74.20.--z, 74.80.--g, 71.38.+i