Yes, we can get responsive ad codes from adsense. But that will not fulfill the requirement for ad unit size per screen size. To make the adsense ads responsive per screen size we need to modify the code (allowed by google obviously) a bit. Reasons we need to do this can be like, In desktop view the ad appear as leaderboard, but in mobile it becomes a 300×250 square, what you might not want as you might want to show a similar horizontal sized ad in that place even in mobile view.