A method of manufacturing a frequency tunable terahertz transceiver including two separate distributed feedback lasers manufactured in one substrate, includes forming a lower clad layer on the substrate, forming an active layer on the lower clad layer, forming an upper clad layer on the active layer. And interposing first and second diffraction grating layers between the upper clad layers. A diffraction grating is manufactured by etching the first and second diffraction grating layers. The active layer is integrated into a passive waveguide. An electrode is formed on the upper clad layer.