A model is proposed to explain the dependence of the substrate hole current inn‐channel metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) on applied electric field and on oxide thickness. Two types of devices were prepared:n‐channel MOSFETs with gate oxides of 67, 86, and 131 A˚ andp‐channel MOSFETs in which gate oxide thicknesses were almost equal to those in then‐channel MOSFETs. The carrier‐separation technique was used in thep‐channel MOSFETs, and the average energy of hot electrons entering the silicon substrate was obtained. The average energy of the hot electrons is related to the energy distribution of hot holes created by hot electrons emitted from the oxide into then+polysilicon gate during the Fowler–Nordheim electron tunneling in then‐channel MOSFETs. The substrate hole current is numerically modeled as thermionic emission of the hot holes overcoming the energy barrier at the oxide‐n+polysilicon interface. For the gate oxides ranging from 67 to 131 A˚, the dependence of the substrate hole current on the electric field and on oxide thickness is explained by using the average energy of the hot electrons and the thermionic hole emission model. ©1995 American Institute of Physics.