Ferroelectric 0.3Pb(In1/2Nb1/2)O-3-0.38Pb(Mg1/3Nb2/3)O-3-0.32PbTiO(3) (PIN-PMN-PT) epitaxial thin films with a perovskite phase were grown on (110)-oriented MgO substrates by sputter deposition method. The structure of the PIN-PMN-PT films was found very sensitive to the growth condition. The single perovskite phase obtained under optimized processing condition was substantially relaxed from lattice-mismatch strain down to at least 11 nm in thickness due to the formation of an ultrathin interfacial layer of twin domains. Compared to other technically important relaxor ferroelectrics such as PMN-PT, the PIN-PMN-PT thin films have a higher Curie temperature and a large coercive field, which are very promising for piezoelectric applications in micro/nano-electromechanical systems. (C) 2015 Elsevier B.V. All rights reserved.