The present invention has the objects to provide a novel material for forming Si-containing film, especially a material containing a cyclic siloxane compound suitable to a PECVD equipment for low dielectric constant insulating film, and to provide an Si-containing film using the same, and a semiconductor device containing those films. The present invention relates to a material for forming Si-containing film, containing a cyclic siloxane compound represented by the following general formula (1) (In the formula, A represents a group containing at least one selected from the group consisting of an oxygen atom, a boron atom and a nitrogen atom, n is 1 or 2, and x is an integer of from 2 to 10.), and its use.