Leakage current model parameters are extracted by non-linear optimization when using a program extractor. Whereas it is often difficult to determine the parameters of a complex model by non-linear optimization alone since it has multi-minimum problems. A new extraction method of poly-Si TFT model parameters in the leakage region is proposed in this paper. It includes two steps: extraction procedure and optimization procedure. In the extraction procedure, the logarithm of X is approximately linear with electric field over a wide range (2 x 10(7)-1 x 10(8) V/m), so the model parameters can be estimated. The extracted results are further optimized in a non-linear optimization procedure. The extraction method is verified with a reasonable agreement between the experimental data and simulated results calculated with the model parameters extracted by our procedure. The total extraction method has been validated by a good agreement after the optimization procedure. In addition, it is easy to implement the extraction procedure in a program extractor. (c) 2007 Elsevier Ltd. All rights reserved.