Semiconductor Equipment Stocks Lose 350 Billion Won in Market Value in One Day

Ultra Clean Holdings (Nasdaq: UCTT) shares plunged 8.33% on the Nasdaq on May 17, closing at $78.78 per share. This drop values the company at roughly $3.5 billion (about KRW 4.6 trillion).

The one-day decline erased approximately $270 million (KRW 350 billion) in market value, with trading volume reaching about 1.07 million shares.

In its Q1 2026 results released at the end of April, Ultra Clean outperformed expectations, reporting revenue of $533.7 million and earnings per share of $0.31. For Q2, it guided revenue of $565.0 million to $650.0 million and EPS of $0.44 to $0.60, underscoring a semiconductor-equipment recovery driven by AI demand.

After more than doubling since the start of the year, valuation pressures and profit-taking have mounted. In May, volatility intensified when the chief information officer sold shares and several analysts warned of potential overvaluation.

Headquartered in Hayward, California, Ultra Clean supplies critical subsystems and components for semiconductor-manufacturing equipment as well as ultra-purity parts cleaning and analytical services to semiconductor firms worldwide.

Highly sensitive to the semiconductor investment cycle, the company posted a significant loss in 2025 due to goodwill impairments and a market downturn. It is now entering a phase in which its performance and valuation are being reassessed amid a rebound in AI-driven equipment demand.