The press articles about this generally are misleading in that they use Silicon-Germanium as the catch phrase that's represents the breakthrough. Whereas in fact SiGe processes have been available for at least a decade. I know this because I developed chips for an IBM SiGe process a decade ago, and in college I did a research paper on semiconductor "superlattices" using an old textbook from our school library. It's not a new technology by any means.

IBM's 7nm is a great accomplishment for sure, but we really don't know anything about how it was made from the articles. Essentially SiGe is a bit more conductive and can switch faster than normal Si chips, thanks to quantum tunneling.