KLA-Tencor's stock experienced a significant pre-market plunge of 10.06%, following the release of its fiscal second-quarter financial results after the previous trading session's close.

Despite reporting quarterly revenue of $3.30 billion and adjusted earnings per share of $8.85, both exceeding market expectations, and providing optimistic forward guidance, the stock price declined sharply. Market analysis indicates the sell-off was driven by investor profit-taking after the stock's rapid appreciation, coupled with concerns over KLA's historically high valuation.

Additional factors contributing to the negative sentiment include the company's revenue growth rate slowing for three consecutive quarters, and while free cash flow remained solid at $1.26 billion, it slightly missed some exceedingly high expectations. The capital market appears to be reassessing the company's future growth resilience amid cyclical fluctuations in the semiconductor industry, with the third-quarter guidance perceived as a "mixed outlook" that failed to demonstrate the strong acceleration anticipated from AI-driven demand.