We detail the design and fabrication technology of two-dimensional photonic crystal (PhC) band edge emitting quantum cascade lasers (QCLs) operating at terahertz frequencies (similar to 3.3 THz). The entire QCL active layer has been deeply etched to form a triangular lattice PhC, in which a complete in-plane photonic band gap for TM polarized light exists. Strong vertical optical confinement is provided by metal-metal plasmon waveguide fabricated with thermocompression bonding and planarization. Benzocyclobutene is employed as a low loss medium to planarize the PhC structure. By tailoring the top metal contact on the planarized PhC structures, electrical current injection pad can also be defined. The lasing properties can be controlled by engineering the photonic band structure. Broad band continuous single mode tuning over 30 GHz was observed; while lower current threshold density and higher operation temperature compared to Fabry-Perot (FP) asers were obtained. (C) 2010 American Institute of Physics. [doi:10.1063/1.3476565]