Patent ID: 8716711

Claim:
A thin-film transistor comprising: a channel layer being formed of an oxide semiconductor transparent to visible light, the channel layer having a refractive index of nx; and a transparent layer disposed in contact with the channel layer and having a refractive index of nt, wherein the transparent layer is disposed in a light-incident side with respect to the channel layer and there is a relationship of nx>nt, wherein the channel layer is formed of an amorphous oxide having a composition represented by the following formula: [(Sn 1 - x M4 x )O 2 ] a .[(In 1 - y M3 y ) 2 O 3 ] b .[(Zn 1 - z M2 z O)] c wherein 0≦x≦1, 0≦y≦1, 0≦z≦1, 0≦a≦1, 0≦b≦1, 0≦c≦1, and a+b+c=1; M4 is a Group 4 element having an atomic number less than that of Sn selected from the group consisting of Si, Ge, and Zr; M3 is Ga; and M2 is a Group 2 element having an atomic number less than that of Zn selected from the group consisting of Mg and Ca.