Shares in South Korean tech giants Samsung Electronics and SK Hynix soared on Thursday, trading at their highest levels in a year after the companies announced partnerships with OpenAI, which drove the country's stock market to a record high.

Samsung Electronics, the crown jewel of South Korea's largest chaebol, rose 4.7% in early trade, its highest level in 52 weeks and the strongest in nearly five years.

SK Hynix, one of the world's largest memory chipmakers, was also trading more than 10% higher – a one-year peak.

The rally helped drive South Korea's benchmark KOSPI index past 3,500 points for the first time in history, adding more than 70 points in morning trade.

The surge followed Wednesday's announcement that both firms had signed preliminary deals with OpenAI to provide chips and other equipment for its Stargate project, during a visit to Seoul by OpenAI chief executive Sam Altman.

OpenAI's memory demand is projected to reach up to 900,000 DRAM wafers per month, which both firms said they would help supply.

SK Hynix said the figure is more than twice the current HBM industry capacity.

Dubbed "Stargate," the OpenAI for Countries initiative was launched in June under the auspices of a drive announced by U.S. President Donald Trump to invest up to $500 billion in AI infrastructure in the U.S.

Altman also met with South Korean President Lee Jae Myung, who said that the OpenAI chief had praised the country as having an industrial base "unmatched by any other," and pledged close cooperation to help it become an AI hub in the Asia-Pacific region.

On Wednesday, separate government data showed South Korea's semiconductor exports hit an all-time high, driven by booming global demand for AI chips.