South Korea's benchmark KOSPI stock index hit an all-time high on Wednesday as SK Hynix joined its memory chip rivals Samsung Electronics and Micron Technology in the $1 trillion market capitalisation club ‌on an ⁠AI-driven rally.The ⁠KOSPI rose as much as 5% to 8,450.26, its highest on record, with the sharp gains triggering a "sidecar" curb that temporarily halted algorithmic trading.Shares of SK Hynix jumped as much as 11.1%, taking the chipmaker's market value to a record 1,624 trillion won ($1.08 trillion).Strong demand for ⁠high-end memory ‌chips used in AI chipsets like those designed by Nvidia has tightened supply and driven up ⁠prices, benefiting the world's biggest makers of the semiconductors.South Korea's Samsung Electronics surpassed $1 trillion in market value for the first time on May 6, while U.S.-listed Micron Technology did so on Tuesday.With Wednesday's rally, which also pushed Samsung Electronics shares up as much as 8% to a fresh record ‌high, the electronics giant and SK Hynix accounted for 50% of South Korea's benchmark index by market capitalisation.The KOSPI, which has ⁠emerged as the world's best performer in a global AI boom, has risen 98% so far this year, after rising 76% last year.Samsung Electronics shares have risen 165% so far this year, while SK Hynix shares are up 245% and Micron Technology shares are up 214%.