The in-situ growth of PbZrxTi1-xO3 (PZT) and PbTiO3 (PT) thin films by reactive sputter deposition has been investigated for applications with silicon substrates. In-situ deposition from three simultaneously operating magnetron sources was applied. At the selected growth temperature range (550-600 degrees C), self-stabilisation of lead composition by a lar ge desorption rate of Pb on stoichiometric PZT surfaces has been observed. Interlayer mixing was found to be limited to a few monolayers. Both Pt and RuO2 on Si-SiO2 wafers were used as top and bottom electrodes. The type of bottom electrode, together with the lead flux and the presence of a bottom PT layer to help nucleate the growth of PZT, was found to have a marked influence on the crystallisation behaviour of the PZT films. Dielectric characterisation has been performed on the films, and the dependence on the deposition parameters is discussed.