Pure perovskite phase, (001)-oriented, epitaxial thin films of (Pb(Mg1/3Nb2/3)O3)0.67-(PbTiO3)0.33 (PMN-PT) were fabricated on single crystal, (001)-oriented SrTiO3 substrates using a hard (Fe-doped) and soft doped (Nb-doped) PZT(52/48) interfacial layer. The effect of different interface layers on the structural and ferroelectric properties of the PMN-PT films was investigated in detail. A significant self-bias voltage in the PMN-PT films can be introduced by using an appropriate interfacial layer. There are significant differences in polarization for different types of doped and undoped interface layers and a doubling of the relative dielectric constant was observed for the Nb-doped interfacial layer. Device properties remain stable up to at least 108 cycles.