| 摘要 |
PURPOSE: A method for forming a contact plug of a semiconductor device is provided to prevent bridge and reduce ohmic contact with a plug when forming a plug using a polysilicon film. CONSTITUTION: A contact plug(24b) of a semiconductor device is formed in such a manner that an insulating film is formed on a semiconductor substrate(20) in which a lower conductive layer pattern is formed, and the insulating film is etched to partially expose the conductive layer pattern so that a contact hole(23) is formed. An upper conductive layer is formed on the insulating film to be buried in the contact hole, and it is then etched back to expose a surface of the insulating film. The insulating film is recessed at a predetermined thickness to project the etched-back upper conductive layer over the insulating film. The projected conductive layer is etched to form a contact plug having a convex shape on its center. At this time, the upper conductive layer is a polysilicon film and the projected conductive layer is etched by sputtering. Preferably, sputtering is performed using one gas selected by a group consisting of Ar gas, a mixing gas of Ar and O2, and a mixing gas of Ar and nitrogen as an etchant. Also, sputtering is performed by isotropic etching in a chamber where reactive ion etching is performed.
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