We developed a technique to prepare highly ordered thin films of organic molecular semiconductors. A quasi single crystalline monolayer of thin film phase pentacene was epitaxially grown on a substrate with a nm scale template prepared by step bunching of Si(111) surface. Band dispersion of the films was measured by angle resolved photoelectron spectroscopy at different temperatures and transfer integrals were derived from tight binding fit to the dispersion observed at 130 K. When the temperature was elevated to 300 K the second derivative plot of the photoelectron spectra became broader and the band dispersion was lost in two directions, whereas the dispersion was still observed in one direction. This finding suggests the anisotropy in phonon scattering, which determines the carrier mobility in the organic semiconductors at room temperature.