The electrical properties, surface morphology and interface characteristics of W/p-diamond contact before and after annealing have been investigated. It is shown that the as-fabricated W/p-diamond contact exhibited non-linear behavior. After annealing at a temperature higher than 400 degrees C, the W/p-diamond contact showed ohmic behaviour. The specific contact resistance of W/p-diamond was 8.2 x 10(-4) Omega.cm(2) after annealing at 500 degrees C for 3 min in a N-2 ambient, which was extracted from fitting the I-V relationship of TLM. It is noted that the RMS roughness increases with the annealing temperature increasing, which could be ascribed to the formation of WOX by the reaction of W and oxygen at high temperature. The XPS measurement showed that the barrier height of the W/p-diamond is 0.45 +/- 0.12 eV after annealing at 500 degrees C. Furthermore, the formation of defects at the W/p-diamond interface, probably created by the formation of tungsten carbide during rapid thermal annealing, should be responsible for the ohmic formation of W/p-diamond after annealing at high temperature. (C) 2018 Elsevier B.V. All rights reserved.