PROBLEM TO BE SOLVED: To inhibit diffusion of a metal element contained in a glass substrate into a gate insulation film or into an oxide semiconductor film.SOLUTION: A semiconductor device comprises: a glass substrate 102; an underlying insulation film 104 composed of a metal oxide formed on the glass substrate 102; a gate electrode 106 formed on the underlying insulation film 104; a gate insulation film 108 formed on the gate electrode 106; an oxide semiconductor film 110 which is formed on the gate insulation film 108 and provided at a position overlapping the gate electrode 106; and a source electrode 114a and a drain electrode 114b which are electrically connected with the oxide semiconductor film 110. A concentration of a metal element contained in the glass substrate 102 in a region at a depth of 3 nm and over from a surface of the underlying insulation film 104 is not more than 1×10atoms/cm.
