U.S. chip stocks tumble on AI financing doubts, China chip surge

U.S. semiconductor stocks extended steep losses in premarket trading Tuesday, building on Monday's sharp decline. Memory-chip makers Micron, SanDisk, and Western Digital each fell about 4%; Intel shed 3.2%; AMD dipped more than 3%; Applied Materials and Marvell Technology each lost about 2.8%; and Super Micro Computer slipped 2.9%. The rout began Monday when Nvidia shares fell 5% in New York, costing the AI chip giant its title as the world's most valuable listed company. The drop came after The Wall Street Journal reported that Nvidia is in talks to provide around $250 billion（約40兆円） toward a massive data-center project tied to OpenAI. Apple overtook Nvidia, which has climbed about 25% so far this year.

The weakness immediately carried into Asian trading Tuesday, as investors pulled back from some of the biggest beneficiaries of the AI boom. South Korea's Kospi tumbled roughly 11%, triggering its eighth circuit breaker of the year; the index was halted after falling 8% and then extended losses to close down 10.8% once trading resumed. Index heavyweights Samsung Electronics and SK Hynix ended the day 13% and 15% lower, respectively. In Japan, the Nikkei 225 fell 4%, with memory-chip maker Kioxia, one of the market's strongest performers in the first half of the year, sinking 18%. SK Hynix, a major supplier of high-bandwidth memory chips to Nvidia and among the biggest beneficiaries of the AI spending surge, was especially exposed to the swings in investor sentiment.

Analysts attributed the pullback to multiple factors: worries over how AI infrastructure is being financed, China's advancing chip capabilities, and intensifying competition from Chinese semiconductor firms. The timing coincided with a stark demonstration of that competitive shift. Chinese memory chipmaker CXMT surged 466% on its Shanghai debut on July 27, in Asia's largest IPO of 2026. The listing raised $8.6 billion（約1.4兆円） and pushed CXMT's market value to 3.3 trillion yuan, or about $487.73 billion（約78兆円）, nearly half the valuation of U.S. rival Micron. This milestone underscored investor concerns that the U.S. semiconductor industry faces both uncertainty about financing its own buildout and rising pressure from well-capitalized Chinese competitors.

The semiconductor selloff reflects a confluence of structural doubts about the AI buildout. Investors have grown uneasy about the financing model underpinning the industry's infrastructure expansion — Nvidia's reported $250 billion（約40兆円） commitment to an OpenAI-linked data-center project crystallized this concern and triggered a broad reassessment of AI equities. Simultaneously, the competitive landscape is shifting: CXMT's stunning 466% debut on July 27, raising $8.6 billion（約1.4兆円） and achieving a $487.73 billion（約78兆円） valuation nearly half of Micron's, signals that Chinese chipmakers are no longer peripheral players but capable of mobilizing capital and market confidence at scale. This dual pressure — uncertainty over how U.S. firms will finance infrastructure and the emergence of well-capitalized Chinese competitors — has pulled investor appetite away from even the strongest beneficiaries of the AI boom, such as SK Hynix, which supplies critical high-bandwidth memory to Nvidia.

The regional contagion illustrates how tightly linked global semiconductor and AI investors have become. The Monday U.S. decline cascaded into Tuesday Asian trading, where circuit breakers were triggered and major chip-heavy indices like South Korea's Kospi fell 11%. The breadth of the selloff — affecting memory makers, logic chipmakers, equipment suppliers, and foundries — suggests this is not a sectoral wobble but a reckoning about the fundamental terms under which the AI boom is being built and who will ultimately profit from it.