Recently,transparent amorphous oxide semiconductors such as Ga-In-Zn-O (a-GIZO),In-Sn-O (ITO),Zn-O (ZnO),In-Ga-O (IGO) are expected for channel materials in liquid crystal displays because its high field effect electron mobility ～10 cm2/V s,low deposition temperature and optical transparency,which is the good candidate for channel layer instead of amorphous Si semiconductor.