Direct comparison of the characteristics of a Si metal‐oxide‐semiconductor device provided by Monte Carlo simulation and experimental results is rare. This paper appraises the degree of agreement between simulated and experimental results of drain current versus drain voltage (Id‐Vd). It also derives the impact ionization rate formula inversely by comparing the simulated and experimental dependence of the substrate current (Isub) on the gate voltage (Vg). We found that (1) forId‐Vdcharacteristics, the agreement in the linear region was off, but overall agreement was fairly good, and (2) the simulatedIsub‐Vgcharacteristics were in fairly good agreement with the experimental characteristics when the modified Keldish formulaPii=P0[(E−1.12)/1.12]nwith annof 7 andP0of 2.8×1011s−1was used as the formula for the impact ionization rate.