WE CLAIM: -
1. A field-effect transistor, comprising at least:
a substrate; a source electrode;
a drain electrode;
a gate electrode;
a semiconductor layer in contact with said source electrode and with said drain electrode; and
a gate insulating layer insulating between said semiconductor layer and said gate electrode;
wherein said semiconductor layer contains a carbon nanotube, and
wherein said gate insulating layer contains a polymer having inorganic particles bound thereto.
The field-effect transistor according to claim 1, wherein said gate insulating layer has a relative dielectric constant within the range of at least 5 and up to 20.
The field-effect transistor according to claim 1 or 2, wherein said polymer contains a polysiloxane.
The field-effect transistor according to claim 3, wherein said polysiloxane has at least a structural unit represented by the general formula (1):
[Chem. 1]
wherein, in the general formula (1), R1 represents a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an aryl group, a heteroaryl group, or an alkenyl group;

R2 represents a hydrogen atom, an alkyl group, a cycloalkyl group, or a silyl group;
m represents 0 or 1; and
A1 represents an organic group including at least two groups selected from a carboxyl group, a sulfo group, a thiol group, a phenolic hydroxy group, or a derivative of these groups, wherein, when said derivative is a cyclic condensed structure formed by two of said carboxyl group, said sulfo group, said thiol group, and said phenolic hydroxy group, A1 represents an organic group having at least one said cyclic condensed structure.
The field-effect transistor according to any one of claims 1 to 4, wherein said carbon nanotube includes a carbon nanotube composite having a conjugaled polymer attached to at least part of the surface of said carbon nanotube.
The field-effect transistor according to any one of claims 1 to 5, wherein said inorganic particles include a metal oxide.
The field-effect transistor according to any one of claims 1 to 6, wherein said inorganic particles have a number-average partiele size in the range of at least 1 nm and up to 100 nm.
The field-effect transistor according to any one of claims 1 to 7, wherein the inorganic particles in said gate insulating layer have a volume fraction in the range of at least 10 vol% and up to 60 vol%.
The field-effect transistor according to any one of claims 1 to 8, wherein said gate insulating layer has a thickness in the range of at least 10 nm and up to 1000 nm.
The field-effect transistor according to any one of claims 1 to 9, wherein said source electrode and/or said drain electrode include(s) an organic binder and an electric conductive powder.
The field-effect transistor according to any one of claims 1 to 10, wherein said field-effect transistor has an on-current of at least 5 uA and a leak current of up to 50

pA.
12. A method for producing the field-effect transistor according to any one of
claims 1 to 11, the method comprising the steps of:
forming, on a substrate, an electric conductive pattern serving as a gate electrode;
applying a solution including at least a polymer having inorganic particles bound thereto onto said substrate having said electric conductive pattern formed thereon, foliowed by drying said solution, to obtain a doating film; and
forming, on said coating film or a gate insulating layer formed by curing said coating film, a semiconductor layer including a carbon nanotube and an electric conductive pattern serving as a source electrode and a drain electrode, in such a marmer that said semiconductor layer and said electric conductive pattern are in contact with each other.
13. The method for producing the field-effect transistor according to claim 12,
wherein said solution including said polymer having inorganic particles bound
thereto comprises a photosensitive organic component, and wherein said method
further comprises the steps of:
irradiating a film with active actinic light via a photomask, said film being obtained by applying, onto said substrate having said electric conductive pattern formed thereon, said solution including said polymer having inorganic particles bound thereto and said photosensitive organic component, and by drying said film; and forming, on said electric conductive pattern, an insulating pattern having an opening, using an alkali solution; and
heating said insulating pattern to form said gate insulating layer having an opening.
14. A wireless communication device comprising the field-effect transistor
according to any one of claims 1 to 11.

15. A goods tag comprising the wireless communication device according to claim 14.