The crystallization behavior of chemical-solution-deposited and amorphous Ba0.7Sr0.3TiO3 (BST) thin films was analyzed with respect to the evolution of the structural and dielectric properties of the films as a function of the annealing temperature. The amorphous films were produced by oxygen ion implantation into crystalline BST thin films, In the amorphous thin films, the crystallization to the perovskite phase occurred at T = 550 degrees C, whereas the as-deposited CSD films showed the first crystalline XRD-reflex only after annealing at T = 650 degrees C. Here a carbon-rich intermediate phase delayed the crystallization process to higher temperatures.