Imagine if Apple, by itself, made up more than 40% of the entire US stock market. That’s essentially what’s happening in Taiwan right now, except the company in question is TSMC. And across the strait in South Korea, Samsung Electronics and SK Hynix together account for 42.2% of the KOSPI. Two countries, three companies, and an AI boom that has turned their stock markets into something closer to semiconductor ETFs than diversified national exchanges.

The KOSPI recently closed at a record 4,457.52, climbing 3.43% in a single session. Taiwan’s benchmark has followed a similar trajectory. The reason is straightforward: the world needs AI chips, and these three companies sit at the center of that supply chain.

The concentration problem nobody minds (for now)

Samsung Electronics has reached a $1 trillion market cap, propelled by surging demand for AI-related memory chips. SK Hynix, which manufactures the high-bandwidth memory (HBM) chips that power Nvidia’s data center GPUs, has seen its stock price surge alongside it. Together they represent 42.2% of the KOSPI.

Taiwan’s situation is even more extreme. TSMC, the world’s dominant contract chipmaker, now constitutes over 40% of the island’s total market capitalization. Every major AI chip designer, from Nvidia to AMD to Apple, relies on TSMC’s fabrication plants to turn silicon wafers into functioning processors.

Asian markets tied to AI outperformed global markets by over 5 percentage points last year. That gap reflects a simple reality: the physical infrastructure of artificial intelligence, the chips, the memory, the advanced packaging, is overwhelmingly manufactured in East Asia.

Why these three companies, and why now

TSMC manufactures the most advanced logic chips on Earth. Its 3-nanometer and upcoming 2-nanometer process nodes are years ahead of competitors. Intel has been trying to catch up. GlobalFoundries exited the cutting-edge race entirely.

Samsung plays a dual role. It fabricates chips and manufactures memory. Its DRAM and NAND flash products feed the insatiable appetite of AI data centers. The company’s push into HBM chips, the stacked memory modules essential for training large language models, has become a major growth driver.

SK Hynix secured early contracts with Nvidia for its HBM3E chips, giving it a head start in what has become the hottest product category in semiconductors.

Hyperscale cloud providers like Microsoft, Google, Amazon, and Meta have committed hundreds of billions in combined capital expenditure for AI infrastructure. That money flows directly into orders for chips, which flows directly into the revenues of these three companies, which flows directly into Korean and Taiwanese stock indexes.

What this means for investors

The bull case is obvious: AI demand is real, it’s growing, and the companies benefiting most happen to be publicly traded on exchanges that give them enormous index weight. Buying the KOSPI or Taiwan’s TAIEX is, in practice, buying a concentrated AI semiconductor position with some diversification on the side.

Concentration cuts both ways. When these stocks rise, they lift entire markets. When they fall, they drag everything down with them. Any investor holding broad Korean or Taiwanese index funds should understand that they’re not getting the diversification the word “index” usually implies. They’re making a directional bet on chip demand.

For global investors, the practical takeaway is this: exposure to Korean and Taiwanese equities is no longer a play on “Asian growth” or “emerging market diversification.” It’s a semiconductor trade, concentrated in three names, driven by a single technological trend.