The invention provides a preparation method of a
metal oxide semiconductor (MOS) device, which comprises the following steps of: firstly, providing a substrate, forming a
gate oxide layer on one side of the substrate, then injecting
deuterium plasma or
fluorine plasma between the substrate and the
gate oxide layer by adopting a decoupling
plasma injection method, and finally, carrying out annealing treatment. The
deuterium plasma or the
fluorine plasma is bonded with
silicon between the substrate and the
gate oxide layer to generate a
silicon-
deuterium bond or a
silicon-
fluorine bond with higher
bond energy; according to the decoupling plasma injection method, the injection depth and the injection amount of the deuterium plasma or the fluorine plasma can be well controlled, annealing treatment is performed after the deuterium plasma or the fluorine plasma is injected, and deuterium or fluorine can replace
hydrogen to form a silicon-deuterium bond or a silicon-fluorine bond with the silicon between the substrate and the gate
oxide layer, and the
bond energy of the silicon-deuterium bond or the silicon-fluorine bond is larger than that of a silicon-
hydrogen bond. And silicon-
hydrogen bond fracture and hydrogen
diffusion at the interface of the gate
oxide layer and the substrate are improved, so that the
negative bias temperature instability effect of the MOS device is improved.