Huawei was known to have been stockpiling chips from its HiSilicon unit before TSMC cut ties to comply with US sanctions. TSMC started making 7 nanometer chips back in 2017.
The costs are higher using the older process DUV machines instead of EUV machines. The costs are probably 30-50% higher. However, the fact that China can make these 7 nanometer chips at all is a huge creative achievement. This is what the global semiconductor industry would have had to do if EUV (Extreme Ultraviolet) machines were not successfully made about 8 years ago. China will be able to make 5 nanometer chips in about 2 years. It will be too difficult to push DUV (Deep ultraviolet (DUV) lithography) machines to achieve 3 nanometers or less.
Huawei and Semiconductor International Manufacturing Corp (SMIC) declined to provide details. Based on tests conducted on the smartphone, Chinese benchmarking website AnTuTu identified the central processing unit (CPU) in the Mate 60 Pro as the Kirin 9000s from Huawei's chip design unit HiSilicon.
Research company TechInsights (based in California) said in a note on its WeChat account that SMIC has used existing equipment and applied its second-generation 7-nanometer process, known as the N+2 node, to manufacture the 5G-capable Kirin 9000s for Huawei.
Another possibility is Huawei built a secret chipmaking supply chain by recruiting existing foundries to help it skirt US export controls. In this case, the chip inside the Mate 60 showcases how Huawei has achieved a breakthrough.