Abstract: As microelectronic devices continue to miniaturize and accelerate, self-heating effects have progressively become a crucial factor limiting their performance enhancement. A deep understanding of the heat generation mechanisms at the nanoscale is of great significance for the design and optimization of electronic devices. In this study, an electro-thermal simulation was conducted for the Silicon-On-Insulator Metal-Oxide-Semiconductor Field-Effect Transistor (SOI-MOS), where the drift-diffusion model was used to thoroughly compute and analyze the generation and effects of Joule heat, recombination heat, and Peltier-Thomson heat. The results revealed that Joule heat is the primary source of power consumption within the device, mainly located beneath the gate in the conductive channel, with its peak value at the drain end. In comparison, the magnitude of recombination heat is minimal, primarily distributed in the channel region and source-drain junction, exerting a weak impact on the temperature field and device performance. The Peltier-Thomson heat, having a comparable heat generation level to Joule heat, affects the device's temperature distribution. However, due to its unique alternating cold and heat source distribution beneath the gate, its heating and cooling effects offset each other, and the temperature changes it induces are concentrated below the source and drain electrodes, resulting in negligible effects on device performance. Furthermore, the impact of Peltier-Thomson heat is related to boundary conditions; when considering heat dissipation from the base, overlooking the Peltier-Thomson heat can lead to significant deviations in temperature field predictions, which is vital for evaluating the lifespan and reliability of the device.