# Why memory chip stocks are rallying again: Micron and Sandisk surge as AI optimism returns > Source: > Published: 2026-07-31 12:58:00+00:00 Memory chip stocks are rallying big after a week of poor performances. Companies including Micron Technology (Nasdaq: MU) and Samsung Electronics Co. (KSE: [005930.KS](http://005930.ks)) saw their shares rise on Thursday, July 30, and into premarket trading Friday, July 31. South Korea’s Kospi (Korea Composite Stock Price Index) recovered and then some from its [fall earlier this week](https://www.fastcompany.com/91581598/kospi-stock-crash-why-sk-hynix-samsung-down-ai-fears), jumping almost 18% on Friday. Its growth was led by a similar turnaround from Samsung and Sk Hynix Inc. (KSE: [000660.KS](http://000660.ks)), jumping 26.81% and 29.95% on Friday, respectively. Meanwhile, American chip manufacturers saw similar turnarounds as the week ended. Still, the boosts weren’t enough to make up for a month of falling stock prices. Here’s where the companies stand as of today: **Micron Technology, Inc. (Nasdaq: MU)** **Sandisk Corporation (Nasdaq: SNDK)** **Western Digital Corporation (Nasdaq: WDC)** **Seagate Technology Holdings (Nasdaq: STX)** All premarket figures are as of publication. All of the chip manufacturers had suffered earlier in the week from ongoing [fears around AI over-investment](https://www.fastcompany.com/91551762/stock-market-ai-bubble-recent-warning-sign-sp-500-mag-seven). But their fates changed—at least for the moment—thanks to strong earnings reports from Microsoft, Amazon, and Lam Research across late Wednesday and Thursday. The tech giants beat expectations on the strength of their cloud growth, indicating that chip demand will continue to be strong. For instance, Amazon Web Services (AWS) [grew its net sales by 37%](https://ir.aboutamazon.com/news-release/news-release-details/2026/Amazon-com-Announces-Second-Quarter-Results/), its quickest growth since 2021. Microsoft’s own cloud computing services, Azure, saw [more than $100 billion in revenue](https://www.microsoft.com/en-us/investor/earnings/fy-2026-q4/press-release-webcast) for the first time. Microsoft 365 Copilot also surpassed 30 million paid seats. In its earnings report, the company stated that the milestones reflect “the confidence customers are placing in us to power their [AI](https://www.fastcompany.com/section/artificial-intelligence) transformation.” Meanwhile, [Lam Research’s revenue](https://investor.lamresearch.com/quarterly-results) rose more than 15% from last quarter “as AI-driven demand continues to reshape the semiconductor industry,” CEO Tim Archer said in the release. Shares of Microsoft (Nasdaq: MSFT), Amazon (Nasdaq: AMZN), and Lam Research (Nasdaq: LRCX) also rose significantly in response to the earnings reports.