To provide a semiconductor thin film having no influence of defects in a grain boundary and catalyst metal and impurities contained in crystal silicon, in a semiconductor element such as a thin film transistor formed by crystal silicon.

In this semiconductor thin film in which a first crystal silicon layer 102 is formed on a substrate, and a second crystal silicon layer 103 is formed on the first crystal silicon layer 102, the second crystal silicon layer 103 is formed by epitaxial growth so as to inherit crystallinity of the first crystal silicon layer 102, and an amount of impurities contained in the second crystal silicon layer 103 is less than that in the first crystal silicon layer 102, and a large number of hydrogen or halogen elements are contained in it.