The ETF market is pushing the limits of the leverage it can handle. SK Hynix is the latest example

The exchange-traded fund market has experienced a three-decade boom led by low-cost, tax-efficient, core index fund investments. But many recent big winners have been single-stock ETFs levering up both bullish and bearish bets on momentum plays, typically tech stocks, such as SpaceX and Nvidia. Single-stock ETFs offering leverage on the latest chip company to hit the market, South Korea's SK Hynix, are anticipated next week, and an ETF expert warned CNBC that these types of trades are "getting a little carried away." Next week, several exchange-traded fund companies plan to hit the market with the latest ETFs, offering a way to add leverage to bets on single stocks, in this case, on the South Korean chip giant SK Hynix, which began trading in the U.S. on Friday. The development should come as no surprise: similar SK Hynix portfolios are already among the most popular ETF trades in South Korea's market. And there is nothing inherently wrong with the planned SK Hynix ETFs coming to the U.S. from companies including GraniteShares and ProShares. Demand for the stock — which has effectively been off the radar of most U.S. investors without a domestic listing — is "enormous," the company's chairman told CNBC. Many existing single-stock ETFs trading on the biggest tech companies in the U.S. operate normally, day in and day out, covering all the Magnificent 7 tech companies, including Nvidia, Apple, Tesla and, most recently, SpaceX, which fell below its first day of trading open price earlier this week and is now down roughly 8% since its IPO, not uncommon for a new issue.