KLA-Tencor (KLAC) experienced a sharp 12.12% 24-hour plunge, as strong fiscal fourth-quarter results and an upbeat revenue forecast were overshadowed by investor disappointment and a broader sell-off in semiconductor equipment stocks.

The decline was triggered by the company's earnings release. While KLA reported Q4 revenue of $3.66 billion, beating the $3.60 billion estimate, and adjusted EPS of $1.05, surpassing the $1.00 consensus, the results failed to satisfy elevated market expectations. Shares fell in extended trading after the report, with multiple news sources noting that the results were not "eye-popping" enough to counter the market's bearish narrative. The company's Q1 earnings guidance, with GAAP diluted EPS of $1.14, also appeared to disappoint investors who had been hoping for blowout results.

Compounding the post-earnings drop, the stock had already fallen over 6% during the regular trading session, pressured by declines across the semiconductor equipment sector. Analysts highlighted that KLA's year-to-date surge of over 57%, driven by AI infrastructure demand, had set a high bar, leading to profit-taking when the report did not significantly exceed forecasts. A Goldman Sachs note expecting the stock to trade lower after the results, along with target price cuts from Deutsche Bank and UBS, further reflected institutional caution and contributed to the negative sentiment.