Semtech is trading at $142.50, +4.63% in after-hours trading, amid a broader risk-on backdrop. - On October 20, U.S. indexes finished higher: the S&P 500 rose 0.66% and Nasdaq gained 0.94%. - Semtech-related coverage mentioned an expanded Tower Semiconductor partnership to secure silicon germanium capacity for AI data-center components, but did not establish the partnership as the cause of this after-hours move.