Spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) are applied to the chemical characterization of very thin films (200–250 Å) of BiSrCaCuO fabricated in a two-step process. Amorphous and insulating films are deposited on (001) MgO single crystals by the laser ablation technique (Nd:YAG laser equipped with a frequency-doubling crystal). Although quasi-congruent for the cations, the ablation process induces an oxygen depletion from the stoichiometric superconducting Bi 2Sr 2CaCu 2O 8 target. Indeed, the surface sensitive X-ray photoelectron spectroscopy (XPS) evidences the presence of a Bi°/Bi(III) mixture as well as the occurence of Cu(I) alone in the deposited film, instead of Bi(III) and Cu(II) as in the parent target material. Core level binding energies of Column II elements are characteristic of their ionic compounds (oxides and carbonates). A large amount of Cu(I) present in the film depth is confirmed by the more bulk-sensitive soft X-ray absorption spectroscopy (XAS) at Cu 2p threshold, operated in the secondary electron total yield mode. The films need to be annealed in 1 atm O 2 at a temperature of 865°C, so that they are converted to the ordered and highly textured Bi 2Sr 2CaCu 2O 8 superconducting phase with T c( R=0)=82 K. After the O 2 annealing, XPS indicates a noticeable decrease of the carbonate content. All the bismuth is reoxidized to Bi(III). Cu(I) is also partly converted to Cu(II). In depth, as shown by XAS, there is a complete conversion to Cu(II), which is the oxidation degree of copper in the superconducting material. Remarkably, a part of the spectral weight of Column II elements and oxygen XPS core levels shifts towards smaller binding energies, which is interpreted in terms of the formation of the metallic lamellar compound. It is shown that an ill-reacted insulating compound remains in the outermost layer.