The present invention provides a high quality thin film comparable to a
bulk single crystal and providres a semiconductor device with superior
characteristics. A channel layer 11, for example, is formed of a
semiconductor such as zinc oxide ZnO or the like. A source 12, a drain 13,
a gate 14 and a gate insulating layer 15 are formed on the channel layer
111 to form an FET. For a substrate 16, a proper material is selected
depending on a thin film material of the channel layer 11 in consideration
of compatibility of both lattice constants. For example, if ZnO is used
for the semiconductor of the channel layer as a base material,
ScAlMgO.sub.4 or the like can be used for the substrate 16.
