A conductive barrier, useful as a ferroelectric capacitor electrode, having high temperature stability has been provided. This conductive barrier permits the use of iridium (Ir) metal in IC processes involving annealing. Separating silicon substrate from Ir film with an intervening, adjacent, tantalum (Ta) film has been found to very effective in suppressing diffusion between layers. The Ir prevents the interdiffusion of oxygen into the silicon during annealing. A Ta or TaN layer prevents the diffusion of Ir into the silicon. This Ir/TaN structure protects the silicon interface so that adhesion, conductance, hillock, and peeling problems are minimized. The use of Ti overlying the Ir/TaN structure also helps prevent hillock formation during annealing. A method of forming a multilayer Ir conductive structure and Ir ferroelectric electrode are also provided.