United Microelectronics is trading 4.26% up at $26.29 on October 2, 2026, as semiconductor shares rally after Micron’s strong results and outlook reinforced optimism about AI-chip demand. - The sector trend is also supported by ON Semiconductor’s revised all-cash Synaptics bid. - No clear new company-specific announcement explains the move; August sales growth and expectations for higher utilization provide background, not a new catalyst for this session.