As a simulation technique for a semiconductor device having a large-scale structure there is a technique referred to as a TCAD (technology CAD (computer aided design)) technique. The TCAD technique mainly comprises a process simulation technique for simulating how a semiconductor device is processed in a manufacturing process, and a device simulation technique for simulating operating characteristics of the semiconductor device.
However, the problem is that a great amount of time is required for the calculation of impurity diffusion in a process simulation, and that the simulation accuracy for the calculation of impurity diffusion is decreased if the calculation time is reduced.