SEOUL, July 8 (Reuters) - Shares of South Korean memory chipmakers Samsung Electronics ( SSNLF ) and SK Hynix fell as much as 4.4% and 5%, respectively, in early trade on Wednesday, tracking a broad selloff in U.S. semiconductor stocks on growing concerns about the sustainability of the AI-driven chip boom.

High-flying memory and semiconductor stocks tumbled overnight, with Intel ( INTC ), Micron and AMD closing down 9.7%, 4.7% and 6.5%, respectively. [MKTS/GLOB]

Also, the Philadelphia Semiconductor Index lost 4.7% as investors questioned whether AI-related spending can be sustained.

The selling was triggered by Samsung's second-quarter preliminary earnings on Tuesday, after the chipmaker's estimate of a 19-fold jump in quarterly operating profit failed to satisfy investors' lofty expectations despite robust demand for AI memory chips.

Samsung's shares tumbled, fuelling a broader retreat from AI-related investments that later spread to Wall Street.

By 0037 GMT, however, Samsung pared losses to trade down 2.3%, while SK Hynix had reversed course to rise 0.2%, outperforming the benchmark KOSPI, which was down 1.4%.