They are processed like any other poly, i.e. they are real existent. That's the best way to provide a consistent environment in the surroundings - as well as relieving STI stress (mainly due to the additional distance).
poly is formed by Uv light. duo to diffraction at grid of UV light. another gate will form near to actual gate . to avoid that we r placing dummy poly . this will cancel the additional poly by distractive interferes
Re: Double dummy poly in deep submicron technologies
193nm lithographic process near UV light grid light will diffracted, so UV will go and form gate at some other place. If drain or source will come that place additional device will form with DRC. to avoid that we add dummy poly . Due to distractive interference it will cancel each other