Samsung Electronics reported one of the strongest quarterly performances in its history, posting an operating profit that surged more than 1,800% from a year earlier as demand for artificial intelligence chips fueled record revenue. Yet the blockbuster earnings failed to reassure investors, with the company's shares falling nearly 7% as markets shifted their attention from current profits to questions about whether the AI investment boom can continue.

The South Korean technology giant said preliminary operating profit for the April-to-June quarter reached 89.4 trillion won, or approximately $58.4 billion, compared with 4.7 trillion won during the same period last year. Revenue climbed to 171 trillion won from 133.9 trillion won in the previous quarter, while sales more than doubled year over year, reflecting robust demand for advanced memory chips used in AI data centers and high-performance computing systems.

Despite the record-breaking financial performance, Samsung's stock closed sharply lower Tuesday as investors appeared to focus less on the company's current earnings and more on the sustainability of the artificial intelligence-driven semiconductor cycle that has propelled the industry over the past two years.

Analysts said much of Samsung's earnings strength had already been reflected in its share price before the announcement.

"The stock had priced in a historic quarter for months, and once the numbers confirmed it was significant but not far beyond what the market had already expected, there wasn't much to reward anyone stepping in," Zavier Wong, market analyst at eToro, told CNBC.

"It acts more like confirmation, and confirmation is what people sell into."

The market's reaction illustrates a broader shift in investor sentiment toward semiconductor companies benefiting from AI. While demand for high-bandwidth memory chips and other advanced components remains strong, some analysts believe hyperscale cloud providers and major AI developers may eventually moderate the pace of infrastructure spending that has supported elevated memory prices.

Wong said Samsung's shares were "dragged down by concerns that AI infrastructure spending can't keep growing at the pace that has been driving memory prices."

Beyond questions surrounding future demand, investors are also evaluating rising operating costs. Samsung's second-quarter results include one-time expenses associated with a new labor agreement reached earlier this year after negotiations with employee unions.

Under the revised compensation framework, Samsung agreed to remove its longstanding bonus cap of 1,000% of base salary and will now allocate 10.5% of operating profit toward employee bonuses. The agreement followed weeks of labor protests in which unions argued employees should receive a larger share of the company's record earnings.

Tom Kang, research director at Counterpoint Technology Market Research, said those developments have added to investor concerns.

"A lot of negative news has been building up, so it looks like everyone wants a piece of that profit. The labor union wants it, and the Korean government wants it," Kang told CNBC.

Samsung's long-term investment strategy is also drawing increased scrutiny. The company recently announced plans to build major new semiconductor fabrication facilities in southern South Korea, a project expected to require substantial infrastructure spending because the region lacks the extensive semiconductor supply chain surrounding Samsung's existing manufacturing operations.

Kang noted that the new manufacturing location represents "new ground," meaning Samsung will need to develop supporting infrastructure that already exists around its traditional production hubs. Analysts say those capital expenditures could pressure profit margins even as AI demand remains robust.

Competition within the memory chip industry is also intensifying. This week, rival SK Hynix is preparing for the listing of its American depositary receipts in the United States, a move analysts believe could temporarily redirect investor interest toward Samsung's closest competitor.

"It doesn't help that SK Hynix's ADR listing lands the same week, pulling some of that rotation appetite elsewhere," Wong told CNBC.