SK Hynix just became the third Asian company to cross the $1 trillion market cap threshold. The South Korean memory chipmaker’s shares surged 11-13% on May 27, powered by an AI chip boom that shows no signs of cooling off.

The stock has climbed more than 250% year-to-date in 2026. Over the past year, some reports peg the gains at over 1,000%.

The “Sam-nix” phenomenon

South Korean retail investors have a name for themselves now: “Sam-nix,” a nod to their aggressive accumulation of SK Hynix shares. These local traders have collectively poured nearly ₩20 trillion, roughly $13.2 billion, into net purchases of the stock.

That buying spree has served as a counterweight to foreign investors who have been taking profits on the way up.

South Korea’s retail trading community comprises roughly 14 million individuals. To put that in perspective, the country’s total population is around 52 million, meaning more than one in four South Koreans is actively trading stocks.

The retail influx has been instrumental in pushing the KOSPI index to record levels. SK Hynix, alongside Samsung Electronics, now accounts for nearly half of the entire KOSPI index.

Why AI memory is the hottest chip on the planet

The company reported revenue of approximately 97 trillion won for full-year 2025, with operating profit roughly doubling year-over-year. First quarter 2026 results reinforced the trend, with AI semiconductor sales driving the bulk of the momentum.

The product at the center of all this is high-bandwidth memory, or HBM. These are specialized memory chips designed to sit next to AI accelerators in data centers, feeding them data fast enough to keep up with massive language models and training workloads.

HBM chips now constitute a growing share of SK Hynix’s DRAM revenue. The company has positioned itself as a primary supplier to major US technology firms that are spending aggressively on AI infrastructure, including Nvidia, Google, and Microsoft.

Analysts predict the AI memory market cycle could last for several years, underpinned by ongoing Big Tech capital expenditure. Advanced memory production faces real constraints, and SK Hynix’s lead in HBM technology gives it pricing power that commodity chipmakers rarely enjoy.

What this means for investors

Samsung Electronics and SK Hynix together representing nearly half the KOSPI index means the broader Korean market has effectively become a leveraged bet on AI memory demand.

Foreign investors are already booking gains. Retail traders have had to absorb $13.2 billion in selling pressure to keep the rally going.