  The h+, h_A1 form factors for the semi-leptonic B->D and B->D* decays are
evaluated in quenched lattice QCD with beta=6.2. The action and the operators
are fully O(a) non-perturbatively improved. The Isgur-Wise function is
evaluated and fitted to extract its slope; the latter is found to be
rho^2=1.1(2)(3) from the B->D* decay and rho^2=1.0(2)(3) from the B->D decay.
The form factors ratios R_1, R_2 are evaluated and found to be in agreement
with experimental determinations.
