The extent to which such an approach has been taken in reality is unclear. However, as pointed out in Dr. Strangelove, a Doomsday Device is only useful as a deterrent if the potential attacker knows of its existence. As soon as it needs to be used, it has already failed its purpose. Hence, there is no reason to keep the existence of such a device secret and every reason to publicize it. Therefore, we can be pretty sure that this is not yet an approach the major superpowers have taken.
