Apple just bought into UMC (United Microelectronics Corporation), a major semiconductor foundry based in Taiwan, which holds several key tech patents and manufacturing facilities that could very well materialize into a full-time foundry for Apple's SoCs, in the future (it currently lacks that capacity). The extent of Apple's investment into UMC is not known, but it's rumored to be "significant." The more popular semiconductor company from Taiwan, TSMC, holds the capacity Apple needs, but lacks the 'flexibility' it wants.
Although Apple sources CPUs from Intel, and GPUs from NVIDIA and AMD, for its Mac product line, it relies on its own SoC designs for its iOS devices, which are contract-manufactured by various foundries, since Apple is fab-less. The UMC buy-in could change that in a very big way, in the near future.