SK Hynix and Samsung shares surge over 20% as AI rally roars back

South Korea's chip heavyweights SK Hynix and Samsung Electronics soared more than 20% in Seoul on Friday, tracking a sharp rally in U.S. technology stocks after blockbuster earnings from Amazon and Microsoft revived optimism around artificial intelligence spending.

LG Innotek advanced 11.2% and Seoul Semiconductor rose 7.8%.

The rally marked a sharp reversal from this week's bruising sell-off, as semiconductor stocks were battered by concerns over lofty AI valuations and signs of intensifying competition from Chinese memory chipmakers.

The iShares Semiconductor ETF (SOXX) surged more than 8% overnight, as investors piled back into AI-linked chipmakers following stronger-than-expected cloud results from the two U.S. tech giants.

Amazon jumped more than 9% in extended trading after reporting second-quarter revenue that beat analysts' expectations, driven by continued strength in its cloud-computing business. Microsoft had rallied 16% during Thursday's regular session after reporting faster-than-expected Azure cloud growth, reinforcing confidence that AI infrastructure spending remains robust.