SK Hynix’s Seoul-listed shares suffered their steepest one-day decline in nearly two decades on Monday, sliding more than 15 per cent as investors booked profits following the chipmaker’s blockbuster Nasdaq debut days earlier. The pullback wiped out a large chunk of the gains the stock had racked up since it began trading on the US exchange.

SK Hynix’s US-listed shares fell 7.9 per cent to $154.7 in early trading, a sharp reversal after the stock had jumped more than 12 per cent on its Nasdaq debut the previous Friday. The whiplash move underscored how quickly sentiment turned on the memory chipmaker after its rapid rise.

The selloff spread beyond SK Hynix. Rival Samsung Electronics also declined, and the combined drag from the two chipmakers helped drive South Korea’s benchmark Kospi index down 9 per cent, triggering a 20-minute trading halt on the exchange. In the United States, memory and storage peers were hit as well, with Micron Technology down 6.4 per cent, SanDisk down 8.4 per cent and Western Digital down 6.8 per cent, while the Philadelphia SE Semiconductor index lost 3.6 per cent.

Korean stocks extended their losses even after trading resumed, despite President Lee Jae Myung reiterating on Monday that his government would help accelerate chip fabrication projects worth billions of dollars, plans previously outlined by both Samsung and SK Hynix.

Separately, Taiwan Semiconductor Manufacturing Co, the world’s largest contract chipmaker, reported record second-quarter revenue on Monday, up 36 per cent from a year earlier, driven by surging demand for artificial intelligence applications. Revenue for the April-June period came in at $39.62 billion, or T$1.27 trillion, according to Reuters calculations, slightly above the T$1.264 trillion analyst estimate compiled by LSEG from 20 forecasts and within the $39-40.2 billion range TSMC had guided in April.

TSMC said June revenue alone rose 67.9 per cent year-on-year to T$442.68 billion, up 6.2 per cent from the prior month. The company had been due to report the data the previous Friday, but the release was delayed because Typhoon Bavi shut down financial markets in Taipei that day.