Vacuum nanoelectronic devices demand efficient electron emission sources, which is increasingly crucial as devices become smaller and more integrated. We propose a Rapid Thermal Treatment method for Metal-Insulator-Metal electron source insulation layers. Samples were treated at 200°C, 300°C, and 400°C in a nitrogen environment. As a result of thermal treatment, the defects in the dielectric layer decreased, and discontinuous islands emerged on the insulating layer’s surface, which increased local electron strength and decreased the electron emission threshold voltage. Consequently, the electron emission efficiency reached 23.6%.