New Delhi, July 30 -- SEOUL - The companies building the data centers that make large-scale AI possible cannot get enough of a specific type of memory chip. That constraint, invisible in most earnings calls and almost never the subject of a mainstream product announcement, just handed Samsung Electronics its best quarter in company history.

Samsung's Device Solutions division, which makes the memory and logic chips the rest of the technology industry depends on, posted operating profit of 89.2 trillion won in the April-to-June period, a figure that represents more than a 250-fold increase from the same quarter a year ago, when the division was barely generating returns above its own cost of capital. Total company operating profit reached...