Shares of European semiconductor companies opened lower a day after Federal Reserve Chairman Kevin Warsh declined to say whether the central bank needed to consider a rate increase later this month. Tech stocks are increasingly sensitive to rate decisions due to high valuation and debt-funded AI infrastructure spending. Chip stocks skidded Wednesday after Warsh said that anyone expecting the Fed would tolerate inflation running above its 2% goal "would be disappointed." The slide extended into Asia and Europe on Thursday. Shares of Dutch semiconductor-equipment maker ASML Holding and smaller rival ASM International are down 3.7% and 4.8%, respectively. German chip maker Infineon Technologies is down 3.3%. STMicroelectronics shares are down 1.7%. (mauro.orru@wsj.com)