U.S. stock indexes open higher, chip and memory stocks lead gains, SanDisk and Western Digital surge nearly 10%

Claire Weston
Published 2026-06-18About 7 min read

All three major US indexes rose at the open, the Philadelphia Semiconductor Index jumped over 5%, and SanDisk and Western Digital each surged nearly 10% — capital is piling into the chip-manufacturing → storage → AI-compute chain.

01

How much did the indexes gain?

The Dow added 0.28%, the S&P 500 0.84%, the Nasdaq Composite 1.17%, and the Nasdaq 100 1.93%.
Gains widened from the Dow to the Nasdaq 100 → money clearly favored tech-growth names over traditional blue chips.
02

Why did semiconductors rally across the board?

The Philadelphia Semiconductor Index rose 5.38% — several times the broad-index gains.
The catalyst: Trump said Apple would partner with Intel to make chips in the US → Intel surged 7.20%, and the market read the headline as a "made-in-America" policy signal.
This means → the bid went beyond Intel alone. The entire semi chain priced in a domestic-manufacturing premium: TSMC +3.88%, Qualcomm +5.77%, AMD +3.83%, Broadcom +3.93%.
03

Why did storage stocks lead the pack?

SanDisk jumped 9.85%, pushing its market cap near $318 billion; it is now up over 800% year-to-date.
Western Digital gained nearly 10%, Micron 6.6%, Seagate over 4%.
This means → storage is the highest-beta link in this rally. AI training and inference both demand massive data throughput, tying storage demand directly to compute buildout.
04

Did the AI-compute chain follow?

Nvidia rose 1.87% — modest by comparison. The leader sits near highs; incremental capital rotated into higher-beta second-tier names.
Super Micro Computer gained 7.72%, Marvell 8.82% → server assembly and networking-chip plays drew stronger bids.
In plain terms = Nvidia is the undisputed AI core, but the bigger money today went to companies that build around Nvidia.
05

How did mega-cap tech fare?

Meta +0.81%, Apple +1.13%, Amazon +0.78% — firm but muted.
Alphabet dipped 0.17%; Microsoft was essentially flat → big tech was "not a drag" today, not the driver.
06

Who bucked the trend?

SpaceX fell 5.39% after closing down nearly 5% the prior session → two straight days of weakness.
Rocket Lab dropped 5.35%; Tesla slid 1.69%.
This reflects a clear capital rotation: money moved into the "chips + AI" basket and out of the "space + Musk-linked" basket.

Content is for reference only, not financial advice.