Metal induced effects on electrical characteristics in AlGaN/GaN Schottky HEMT are reported. Focus is given to the collapse of drain current attributed to Schottky metal. Of particular interest for discussion is that TiN gate can suppresses the collapse of drain current compared with conventional Ni gate. Nitrogen concentrations in TiN gate are found to be correlated to the current collapse, indicating that the nitrogen vacancy is responsible for the traps in AlGaN/GaN HEMT. The reduction in a concentration gradient of nitrogen should be accomplished for preventing the formation of the traps. Because of the metal dependent collapse of the drain current, the traps are considered to be formed under the gate edge on the drain side in AlGaN layer.