Recently, much effort has been expended on etching platinum film, which is the candidate electrode material for the capacitor structure of future dynamic random access memory and ferroelectric random access memory. One of the most critical problems in the etching of platinum was generally considered to be the gradual character of the etch slope. Therefore, the addition of N2 gas into the Ar/Cl2 gas mixture, which had been proposed as the optimized platinum etching gas combination in our previous article, was performed. The selectivity of platinum to oxide as an etch mask increased with the addition of N2 gas, and a steeper etch slope, over 75°, could be obtained. These phenomena were interpreted as the result of a blocking layer, such as Si–N or Si–O–N, on the oxide mask. Compositional analysis was carried out by x-ray photoelectron spectroscopy and secondary ion mass spectrometry. Moreover, the higher etch rate of the Pt film and a steeper profile without residues (such as Pt–Cl and Pt–Pt) could be obtained by the addition of 20% N2 gas in the Ar(90)/Cl2(10) plasma. The plasma characteristics were extracted from optical emission spectroscopy. © 2000 American Vacuum Society.