Patent ID: 8912092

Claim:
A method of forming a semiconductor device, the method comprising: forming a first interconnect structure over a semiconductor substrate, the first interconnect structure comprising a first interconnect and a first insulating film, the first insulating film covering the first interconnect; forming a second insulating film covering the first interconnect structure and the semiconductor substrate; forming a first opening in the second insulating film, the opening exposing the first interconnect structure and the semiconductor substrate; forming a first conductive film in the first opening and over the second insulating film; and carrying out a chemical mechanical polishing process, to form a first contact plug in the first opening, under condition that a first polishing rate of the first insulating film is greater than a second polishing rate of the first conductive film, and that a third polishing rate of the second insulating film is greater than the second polishing rate of the first conductive film, wherein the first interconnect comprises a first bit line, and the first interconnect structure further comprises a second bit line adjacent to the first bit line, and the first opening is positioned between the first and second bit lines.