KLA-Tencor (KLAC) shares tumbled 8.99% in post-market trading, reversing initial gains after the semiconductor equipment maker reported fiscal fourth-quarter results that topped analyst estimates but failed to satisfy elevated investor expectations.

The company posted adjusted earnings of $1.05 per share on revenue of $3.66 billion, both ahead of consensus estimates. KLA also issued first-quarter revenue guidance of $4 billion, plus or minus $200 million, exceeding the $3.92 billion Wall Street forecast. However, the GAAP diluted EPS outlook of $1.14 appeared to disappoint investors who had been hoping for blowout results, triggering a sharp sell-off in extended trading.

Adding to the pressure, the stock had already surged more than 57% year-to-date, driven by strong AI-related demand for its process control tools. With the broader semiconductor equipment sector facing selling pressure and analysts cautioning that the results were not "eye-popping," the post-earnings decline reflected a classic case of profit-taking on high expectations that were not fully met.