We have synthesized vertically aligned carbon nanotube (CNT) emitters on iron-deposited trenches by thermal chemical vapor deposition of acetylene gas for field emission applications. The trenches patterned with various shapes and sizes were fabricated on silicon oxide/silicon substrates using a conventional lithography method and lift-off process. The vertically well-aligned carbon nanotubes were selectively grown only on iron-deposited trenches. The alignment, selectivity, and structure of carbon nanotube emitters grown on the patterned silicon trenches with various shapes and sizes are investigated. Field emission properties such as turn-on voltage and the emission current are also characterized.