The Zen 3-based processors will be made on a 7nm EUV process, there are no firm details about Zen 4 yet.
The "Zen 4" architecture is being designed for a 2021 market debut, and will come out at a time when the 7 nm process will have matured and attained high enough volumes at TSMC for AMD to either build bigger dies (more cores per chiplet), or leverage the even more advanced 6 nm EUV node. The maturity and volumes of these sub-10 nm nodes could change the economics of the MCM approach AMD is undertaking for its EPYC processors.
Via: TechPowerUp