Taiwan is a LONG ways away from Japan. It is not even close.
Buying from Taiwan =/= they are the most advanced. In semiconductors, it is well known that the US is the most advanced. This is not just because of the actual devices produced but because of the process instrumentation and process engineering in these countries. The machines used to fabricate the chips in Taiwan and South Korea are all from US or Japan, made by companies such as Applied Materials and Nikon. And what about testing equipment? Again, most surface testing equipment, memory testing, etc. is all from the US and Japan. As of now, Taiwan and South Korea have very few players in the semiconductor process equipment category. At least there are Chinese companies that are making process equipment and testing equipment.
Some ppl have this mistaked as dependence. There's no dependence - if Taiwan cuts mainland off, then their companies will crash; there's already companies like HiSilicon, Spreadtrum, etc. in the design sector and SMIC, Huahong, etc. in the fabrication sector waiting in the wings ready to substitute their own products. There's also hundreds of labs at academic institutions with the equipment and the intellectual property to quickly form startups if market conditions are right (read, competitors exit the market).