The performance of metal-insulator-metal (MIM) diodes is investigated. In this paper, we derive an analytical model that uses the Transfer Matrix Method based on the Airy Functions (AF-TMM) for the tunneling transmission probability through any number of insulating layers. The fast-computing AF-TMM simulator results show a complete matching with the numerical Non-Equilibrium Green's Function and a reasonable matching with previously published experimental results. This study shows the effect of the work function difference and insulator thickness on MIM diode performance. The advantage of using two insulator layers on enhancing the diode responsivity, resistance, and nonlinearity is also investigated.