We have measured I(V) characteristics of c-axis planar tunnel junctions on
Y1Ba2CU3O7-delta films. Our results and their analysis provide experimental
support for the importance of the two-dimensional character of the YBCO ba
nd structure, and a method to measure the ratio between the Fermi energy of
YBCO and the barrier height. The analysis is based on the relation between
the linear conductance background, related to the inelastic tunneling comp
onent, and the zero bias conductance, related to the elastic one.