1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device.
2. Description of the Related Art
In recent years, efforts have been made to develop a ferroelectric memory that uses a ferroelectric film as a dielectric film for a capacitor. In a ferroelectric memory, noble metal such as platinum is used for capacitor electrodes in order to suppress reaction of the ferroelectric film during crystallization annealing (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 9-162311).
However, a product (noble metal compound) obtained by etching noble metal such as platinum exerts a low saturated vapor pressure. This makes it difficult to appropriately achieve anisotropic etching. Accordingly, appropriate anisotropic etching requires substrate temperature to be increased to about 300 to 400° C. It is thus difficult to use a photoresist as an etching mask. Consequently, anisotropic etching is generally carried out using a hard mask such as a silicon oxide film.
A hard mask is formed by a film forming method such as CVD or sputtering. A film formed by such a film forming method generally adheres well. Consequently, the hard mask cannot be easily removed by the above method.
On the other hand, the reduced size of semiconductor devices has made it difficult to precisely process gate electrodes of MIS transistors by anisotropic etching. To form gate electrodes by anisotropic etching, it is necessary to maximize the etching selective ratio of gate electrode films to gate insulating films.
However, a higher etching selective ratio enlarges the lower part of the gate electrode, which thus has an inappropriate shape. An attempt to reduce the etching selective ratio to improve the gate electrode shape may disadvantageously result in etching the gate insulating film, exposing a semiconductor substrate.
As described above, if an adhesive film such as a hard mask is used as an etching mask to etch an etching target film, removing the etching mask is disadvantageously difficult.
Further, if the etching target film such as the gate electrode film is etched, it is disadvantageously difficult to obtain an appropriate etching processing shape without affecting an underlying film such as the gate insulating film.