Method for forming cylindrical capacitor lower plate in semiconductor device

A method for forming a lower plate of a cylinder type stacked structure capacitor in a semiconductor device, comprising:

• depositing a first insulating film on a principal surface of a semiconductor substrate in which at least one MOS transistor is formed;
• forming a contact hole which penetrates said first insulating film to reach said semiconductor substrate;
• depositing a first conducting film to fill said contact hole and to cover said first insulating film;
• depositing on said first conducting film, a second insulating film which is formed of a silicon oxide film containing at least one impurity selected from the group consisting of V-group elements and III-group elements, and which can be selectively etched against said first insulating film;
• conducting a heat treatment after said second insulating film is deposited;
• forming a resist film on said second insulating film and at a position directly above said contact hole;
• conducting a first anisotropic etching using said photoresist film as a mask, so as to selectively etch said second insulating film, thereby to deposit an etching reaction product and to form a patterned second insulating film in alignment with said resist film;
• removing said reaction product deposited and said resist film;
• etching selectively said first conducting film using said patterned film as a mask, to form a patterned first conducting film in alignment with said patterned second insulating film, and to expose said first insulating film;
• depositing a second conducting film on a whole surface;
• conducting a second anisotropic etching to said second conducting film so that a remaining second conducting film is left only on a side surface of said patterned second insulating film and said patterned first conducting film thereunder, said remaining second conducting film being in contact with said patterned first conducting film;
• and
• selectively removing said patterned second insulating film,
• whereby said patterned first conducting film constitutes a base portion of a cylindrical capacitor lower plate, and said remaining second conducting film constitutes a sidewall portion of said cylindrical capacitor lower plate, said sidewall portion being upright from a periphery of said base portion.