The study proposed a method on a high breakdown voltage for AlGaN/GaN high electron mobility transistor (HEMT). It has a structure of double charge region passivation layer by adding two negative charge regions in the passivation layer between the gate and drain. The negative charge can be realized with fluorine plasma treatments. Compared with the structures of conventional passivation layer and field-plate transistor, the electrons in the channel of the transistor with double charge region passivation layer are depleted by the negative charge in the passivation layer, which would result in increasing ON resistance. Futhermore, there would not be larger peak electric field in the channel layer, and also the electric field is more well-distributed. The Id of this structure has a certain improvement over the one of the field plate structure, and it is less than that of the traditional HEMT. The double charge region passivation layer can regulate the distribution of electric field in the channel layer, which could effectively improve the breakdown voltage of the device to 1200 V.