The relevance of the theoretical Suzuki's model of surface state density to determine the surface state distribution at the active layer/silicon dioxide interfaces is carried out in polycrystalline silicon thin film transistors (TFTs) issued from two different crystallization technologies of the active layer: furnace solid phase crystallized (FSPC) and laser solid phase crystallized (LSPC) TFTs. The experimental validation of this model is demonstrated using the field effect conductance method. Results show that distribution is higher for the FSPC TFTs in relationship with the process crystallization of the active layer. In addition, it is shown that the theoretical surface state model allows discriminating dangling bond state and tail state distributions and acts as relevant model to qualify the surface of thin film material.