Compare with any other semi-conductor shares, TSM is better than most of them, yet still the PE is much lower. So not sure why you say it is expensive.
I would not buy Tiwan Semiconductor at this time. Up over 100 percent in the last 12 months. I would buy if the PE falls in the mid twenties. Very good companies. The current price would imply a big risk. It's a hold or possible sell for me. Long term investors should hold. Traders should sell.