The Philadelphia Semiconductor Index climbed more than 6% on Thursday, its biggest one-day gain in months, as investors seized on Microsoft’s earnings as the clearest evidence yet that the AI computing boom is still accelerating. Equipment makers led the rally, with Lam Research jumping 20% and Applied Materials gaining 12%. Micron rose 10%, AMD and Intel each added about 9%, ASML and TSMC climbed 6%, and Broadcom rose 3%. Nvidia, the sector’s largest stock, gained about 1%.
The trigger was a number in Microsoft’s quarterly filing. The company disclosed more than $130 billion in new data-center lease commitments during its fiscal fourth quarter, pushing its total undelivered lease obligations to $329.1 billion from $196.6 billion three months earlier. Investors read the disclosure as a direct measure of how much computing capacity the largest AI buyer expects to need.
The rally was a sharp reversal of the mood that had gripped chip stocks in recent weeks. A rotation out of AI names and concerns that hyperscalers might trim their buildouts had knocked the index off its highs, and the semiconductor trade had begun to look crowded. Microsoft’s numbers, in that context, were a reassurance: the biggest spenders are spending more, not less.
Equipment makers were the clear winners because they sit at the start of the supply chain. Lam Research and Applied Materials make the tools that fabricate advanced chips, and their revenue depends on capacity additions that are planned years in advance. A jump in cloud lease commitments translates, with a lag, into orders for their machines.
Memory stocks drew the same logic. Micron’s gain reflected the view that AI servers consume far more memory than conventional ones, and that Microsoft’s buildout plans add to an already-tight market. Contract memory prices have risen for four consecutive quarters, and chip analysts said the supply-demand balance favors producers into next year.
The dispersion inside the rally told a subtler story. Nvidia, the company most directly tied to AI, rose the least, a sign that its valuation already prices in the boom. The biggest gains went to companies whose shares had lagged, as investors rotated into the parts of the semiconductor market that had not fully participated.
The read-through extends beyond the chip industry. Microsoft’s lease commitments imply demand for power, cooling equipment and industrial construction for years to come, and analysts pointed to those adjacent markets as beneficiaries of the same trend. Data-center construction has become a significant driver of orders for electrical equipment makers and power utilities.
The gains also reflect a shifting debate inside the market. The question for the past year was whether AI capital spending would plateau. Thursday’s answer, at least for now, is that it is accelerating. Microsoft’s finance chief has said capital spending will keep rising this fiscal year, and Alphabet and Amazon have made similar statements.
The move had a technical element as well. Coming off a stretch of weak performance, chip stocks were under-owned relative to the rest of the AI trade, and Thursday’s catalyst gave institutional buyers a reason to add exposure. Options desks reported heavy call buying in equipment names, amplifying the move.
The risks have not disappeared. Lease commitments are obligations, not guarantees of revenue, and a pullback in AI demand would leave hyperscalers with capacity they cannot use. Some analysts have warned that the industry’s collective spending carries the seeds of its own oversupply, and that the memory and equipment cycles remain brutal when they turn.
The index’s moves were broad but not uniform. Lam Research and Applied Materials, both suppliers of the machines that make chips, led because their revenue lags capacity decisions by a year or more, giving investors a longer runway of visible demand. Their gains, roughly double the index’s average, signaled that the market expects the buildout disclosed this week to translate into equipment orders well into next year.
The rally also lifted the parts of the semiconductor chain that had been left behind. Stocks tied to memory, advanced packaging and even chip-design software gained, as investors mapped Microsoft’s commitments onto every layer of the supply chain. The only major name that barely moved was Nvidia, whose shares had already priced in years of AI growth.
Options markets reinforced the move. Call buying in equipment makers and memory names surged, with dealers forced to hedge by buying the underlying stocks, a dynamic that extended the session’s gains. Traders said the volume suggested institutional repositioning rather than retail speculation, a sign the rally had staying power.
For Thursday, though, the market chose the optimistic reading. The Philadelphia Semiconductor Index’s gain pushed it near record territory, and the breadth of the rally, with every major name in the index rising, suggested conviction rather than a narrow trade. The chip sector has now spent three years arguing over whether AI demand is real; Microsoft’s filing was the latest and largest exhibit that it is.
