Low-resistivity Ni/Pt Ohmic contacts to p-type N-doped ZnO were fabricated in this paper. Ni/Pt Ohmic contacts showed a lowest specific contact resistivity of 3.81 x 10(-6) Omega cm(2) after 450 degrees C annealing, which is lower than any other reported Ohmic contacts to p-type ZnO. The interface reactions during annealing and the Ohmic contact formation mechanism were investigated by secondary ion mass spectrometry measurements. The results showed that Ni out-diffused to react with Pt and Zn out-diffused a little, too. These interface diffusions as well as activation of N acceptors during annealing induced such a low specific contact resistivity. (C) 2010 Elsevier Ltd. All rights reserved.