The semiconductor sector fell in after-hours trading, primarily driven by Intel's disappointing fourth-quarter forecast. After releasing its earnings post-market, Intel (INTC) shares plunged nearly 17% on guidance for revenue and profit margins that fell short of Wall Street expectations, citing a slowdown in the PC market. This negative sentiment was compounded by a significant drop in Marvell Technology (MRVL) shares, which fell over 10% on concerns over its potential acquisition of Lumentum. Broader concerns about AI infrastructure spending, sparked by Alphabet's recent earnings miss, also weighed on the sector.