Semiconductor stocks rallied through September and into early October 2026 because the AI hardware buildout kept producing hard numbers.
The iShares Semiconductor ETF (SOXX) gained 11% in September, Micron reported record revenue with memory supply still tight, and TSMC's September sales rose 54.6% year over year. For US-stock investors, the sector's direction is being set by AI demand data, not by any single headline
The Driver: SOXX Up 11% in September on AI Demand Data
According to The Motley Fool, the iShares Semiconductor ETF gained 11% during September and added another 3.6% in the first two days of October.
The same report credits much of the move to Meta Platforms' mid-September launch of its Muse AI personal agent, which raised expectations that "agentic AI" could create fresh demand for CPUs, memory and related chips.
The Motley Fool also notes that Micron's earnings, which pointed to tight memory supply conditions extending through 2028, reinforced that optimism.
Two company reports supplied the hard data behind the rally:
Data point | Figure | Source |
Micron fiscal Q4 2026 revenue (reported Sept. 30) | $54.23 billion, vs. $41.46 billion prior quarter and $11.32 billion a year earlier | Micron earnings release |
Micron fiscal Q1 2027 revenue guidance | $61.5 billion, plus or minus $1.5 billion | Micron earnings release |
TSMC September 2026 revenue | NT$511.86 billion, up 54.6% year over year, down 0.6% from August | TSMC monthly revenue report |
TSMC January to September 2026 revenue | NT$3,898.73 billion, up 41.1% year over year | TSMC monthly revenue report |
Why It Matters for the Sector: Memory Pricing Power and Foundry Volume
The two reports describe different parts of the same supply chain. Memory makers sell the DRAM and high-bandwidth memory (HBM) that sit beside every AI accelerator, while foundries such as TSMC manufacture the processors themselves.
When both report rising sales in the same weeks, it suggests that AI spending is reaching more than one layer of the industry.
On memory, the key issue is supply. As reported by 24/7 Wall St., Micron CEO Sanjay Mehrotra said the company does "not have line of sight to when supply and demand will return to balance," and that more than 75% of output is already committed for 2027, with HBM largely sold out.
Per Micron's earnings release, Micron's non-GAAP gross margin reached 87.0% in the quarter, a sign of how much pricing power tight supply has given memory producers. This is the same memory chip crunch that has pulled memory names into the wider semiconductor trade.
On manufacturing, TSMC's figures show volume rather than pricing. Per TSMC's monthly revenue report, revenue in the first nine months of 2026 was 41.1% higher than a year earlier.
Because TSMC produces chips for many US-listed designers, its monthly sales are widely read as a gauge of demand across the sector.
Valuation is the other side of the story. According to The Motley Fool, SOXX trades at a price-to-earnings ratio of 43, which means the sector already prices in a great deal of continued growth.
The same Micron report showed how much can be priced in: 24/7 Wall St. reported that Micron shares closed flat at $1,065.11 after the record results, as much of the good news was already reflected in the stock.
Companies in the Story: Micron, TSMC and AMD
Micron Technology is at the center of the memory side of the story. According to its earnings release, full fiscal year 2026 revenue reached $133.19 billion, versus $37.38 billion the year before. Per 24/7 Wall St., the stock had gained 273.42% year to date at the time of the report.
Taiwan Semiconductor Manufacturing (TSMC), whose shares trade in the US as American depositary receipts, is the manufacturing side. Its September revenue figure above is its latest monthly disclosure ahead of full quarterly results.
AMD was among the sector's biggest September movers. According to The Motley Fool, AMD rose 30% in the month, while Intel gained 34%, Micron climbed 11%, Nvidia gained 3% and Broadcom fell 5%.
The spread between those moves shows that the rally was not uniform, and that investors were treating companies differently based on their exposure to the AI demand they expect.
What to Watch Next: TSMC's Q3 Earnings on October 15
The next scheduled sector event is TSMC's full third-quarter report. According to TSMC's investor relations page, the TSMC Third Quarter 2026 Earnings Conference will be held on Thursday, October 15, 2026, at 14:00 Taiwan time (2:00 a.m. Eastern Time).
Points worth watching include the company's comments on AI demand, its margin performance and any update to its outlook for the rest of 2026.
On memory, Micron's next checkpoint is its fiscal Q1 2027 report, measured against the $61.5 billion revenue guidance it has already given. Any change in management's view on how long the supply shortage lasts would be read across the memory group.
Given SOXX's 43 times earnings valuation, results that merely meet expectations may draw a muted reaction, as Micron's own flat close showed.
This article is for education and information only and is not investment advice. Investment decisions are your own after doing your own research.
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