Dependence of electrical properties of phase change Ge1Sb2Te4 thin film on structural transformation was investigated. The electrical resistivity of the film decreases with increasing annealing temperature with a steep drop at similar to 23 0 degrees C (the second crystallization temperature), at which the structure of Ge1Sb2Te4 changes from face-centered cubic to trigonal state. The steep drop of resistivity at the second crystallization temperature is mainly due to the increase of hole density within the p-type film, according to Hall measurement. The crystallization process has been followed by in situ resistance measurement at various annealing temperatures. Transmission electron microscope and atomic force microscope were also employed to study the film. (C) 2007 Elsevier B.V. All rights reserved.