FIELD EFFECT TRANSISTOR USING OXIDE SEMICONDUCTOR AND DISPLAY APPARATUS THEREWITH

A field effect transistor comprises a gate electrode (406), an oxide semiconductor layer (409), a source electrode (410), a drain electrode (410), and an insulating layer (408 and/or 412) being in contact with the oxide semiconductor layer, wherein the insulating layer has a hydrogen content of less than 3 × 10 21 atoms/cm 3 . Such transistor may be used in a circuit board comprising a substrate (400), a wiring (401, 402, 403) and transistors electrically connected to the wirings. Such transistor may also be used in a display apparatus with a plurality of pixels, comprising a transistor (55 and/or 56) provided for each of the plurality of pixels, and wirings electrically connected to each of the plurality of transistors. A method of producing a field effect transistor comprising the steps of: forming a layer including a metal on a substrate (400); pattering the layer including the metal; forming a first insulating layer (408) on the patterned layer (406) including the metal; forming an oxide semiconductor layer (409) in contact with the first insulating layer; patterning the oxide semiconductor layer; forming an electrode layer (i.e., layer which becomes 410) on the patterned oxide semiconductor layer including the metal; and pattering the electrode layer; wherein the first insulating layer is formed so as to have a hydrogen content of less than 3 × 10 21 atoms/cm 3 .