The generation of hot carriers in MOS transistors greatly obstructs their microminiaturization, since this effect becomes more serious in a smaller geometry which creates higher internal electric fields. A two-dimensional simulator of MOSFET has been developed by the authors which includes the generation of hot carriers. the model used takes account of the motion of electrons injected in the gate oxide film. By using this simulator, the device characteristics with an applied voltage stress can be predicted. the simulator has made possible the accurate calculation of the dependency of the gate current on the gate voltage, which could not be solved by conventional simple models. By using this simulator, it is also possible to obtain directly the change of the device characteristics due to the capturing of electrons in the oxide film which is the cause of the channel current, since their distribution now can be obtained. the calculated values of the prediction of the channel current are in good agreement with values obtained experimentally. This simulator is considered to be a useful tool for solving hot-carrier problems in small-geometry MOSFETs.