Lead zirconium titanium oxide (PZT) thin films are used for their ferroelectric and piezoelectric properties. The composition of the PZT is very important for these properties, and may also be influenced by inter- diffusion with the bottom electrode, on which the PZT film has been grown at rather elevated temperature (550°C-600°C). The bottom electrode is essentially made of RuO2 deposited on a chromium adhesion layer which also helps to block oxygen diffusion. A part of the multi-layer device is shown in Figure 1. Since now no comprehensive study concerning rnicroanalysis of the device have been made, the composition of the films as well as the other layers are not precisely known. It is therefore not possible to relate the composition to the functional properties of the device and to optimize the parameters of deposition. It was the aim of this work to study the composition of the Pb(Zr,Ti)O3 layer, and the bottom electrode by mean of energy dispersive X-ray analysis (EDX) and energy electron loss spectroscopy (EELS). The experiments were performed with the Hitachi HF 2000 equipped with a field emission gun located at the EPFL.