The structure that a thin film confined between two materials is widely exists in microelectronic devices.Thermal resistances across the thin film include the thin film resistance and thermal boundary resistances at the two interfaces.When the thickness of the thin film is at the scale of nanometer,these three resistances are coupled with each other and the relationship is seldom discussed in literature.Using molecular dynamics simulations,we systematically investigate the net resistance across the confined thin film.The confined thin films considered in this study including crystalline,amorphous,and alloy with film thickness up to 20nm.Our results indicate that when the thin film is crystalline,the total resistance is smaller than that predicted from thermal circuit model in diffuse limit.In contrast,when the film has structure disorder(amorphous)or mass disorder,net thermal resistance is evidently larger than the prediction from thermal circuit model in diffuse limit,except the cases that the thin film is only a few atomic layers thick.For a mass mixing thin film formed at the interface of two dissimilar materials,our results indicate that when the mass mixing layer is very thin(a few atomic layers),it can reduce the thermal resistance across the interface,regardless the mixing layer is ordered or amorphous.For the cases of disorder thin film,thermal resistance is almost linearly dependent on the thickness and can still be described by the thermal circuit model if a modified thin film thermal conductivity is employed.