Micron, the largest US memory chipmaker, sank 7% in extended trading after forecasting fiscal first-quarter sales of US$7.9 billion (RM32.69 billion) to US$8.3 billion.

That fell short of the average analyst estimate of US$8.45 billion, according to data compiled by Bloomberg.

Competitor Western Digital Corp declined 3%, while semiconductor equipment suppliers Applied Materials Inc and Lam Research Corp fell about 1.5%. Advanced Micro Devices Inc., the sector’s best performer this year, dropped 1%.

Semiconductor stocks, one of the best performing sectors in the last two years, have struggled to make new highs.

While the S&P 500 Index closed at another record Thursday, the Philadelphia Semiconductor Index is down 4% since its March high and has lost ground this month.

Contributing to investors’ angst is Micron’s comment that the trade war between the US and China would hurt profitability in the first quarter.