A thin film transistor substrate and method of manufacturing a thin film transistor substrate through a 3-sheet mask process includes forming a first conductive film on a substrate; forming a gate line including a gate electrode using a first photoresist film pattern formed on the first conductive film through a first mask with a desired pattern formed thereon; sequentially forming a gate insulation film, an active layer, an ohmic contact layer, a second conductive film and a protection film on an entire surface of the substrate; forming an active region and a data line including source-drain electrodes using a second photoresist film pattern that has different thicknesses in predetermined regions and is formed on the protection film through a second mask with a desired pattern formed thereon; forming a contact hole by exposing a channel region of the active layer and partially exposing the source-drain electrodes using the second photoresist pattern; forming a third conductive film on the entire surface of the substrate; and forming a pixel electrode to be connected to the contact hole using a third photoresist film pattern formed on the third conductive film through a third mask with a desired pattern formed thereon. The present invention further provides a liquid crystal display having the same.