We describe the fabrication processes and electrical characteristics of two types of NbN junctions. One is a self-shunted NbN/NbN_x/AlN/NbN Josephson junction, which is expected to improve the density of integrated circuits; the other is an underdamped NbN/AlN_x/NbN tunnel junction with radical-nitride AlN_x barriers, which has highly controllable junction characteristics. In the former, the junction characteristics were changed from underdamped to overdamped by varying the thickness of the NbN_x layer. Overdamped junctions with a 6-nm-thick NbN_x film exhibited a characteristic voltage of V_c =0.8mV and a critical current density of J_c =22A/cm² at 4.2K. In the junctions with radical-nitride AlN_x barriers, J_c could be controlled in the range 0.01-3kA/cm² by varying the process conditions, and good uniformity of the junction characteristics was obtained.