A thin film transistor substrate and a method for fabricating the same are disclosed. A thin film transistor substrate includes a substrate comprising a plurality of grooves having different depths, respectively, to have a multi-step structure; gate and data lines alternatively crossed in the grooves to form a plurality of pixel areas; thin film transistors formed in the grooves of the substrate to be formed in cross portion of the gate and data lines, wherein active layers of the thin transistors are formed along the gate lines and gate electrodes, the active layers separated from active layers of neighboring pixel areas with the data line located there between.