Insulated-gate field effect transistor
In a heterostructure field effect transistor (MISHFET), a source ohmic electrode 105 and a drain ohmic electrode 106 are formed on an AlGaN barrier layer 104. A SiNx gate insulator 108, a p-type polycrystalline SiC layer 109, and a Pt/Au gate electrode 110 being an ohmic electrode are formed one on another on the AlGaN barrier layer 104. Since the p-type polycrystalline SiC layer 109 is relatively large in work function, the channel of the MISHFET is depleted even in its zero-bias state, so that the normally-OFF operation occurs.
1. An insulated-gate field effect transistor comprising:
a semiconductor channel layer in which a first conductive-type channel is formed;
a source electrode formed on the semiconductor channel layer;
a drain electrode formed on the semiconductor channel layer;
a gate insulator formed on the semiconductor channel layer;
a second conductive-type semiconductor film formed on the gate insulator; and
a gate electrode formed on the second conductive-type semiconductor film and made of a metallic ohmic electrode, wherein
the gate electrode made of a metallic ohmic electrode serves as a first gate electrode, and
the insulated-gate field effect transistor further comprises a second gate electrode which is formed of a Schottky electrode formed on the semiconductor channel layer and between the first gate electrode and the drain electrode and which is electrically connected to the source electrode.
2. The insulated-gate field effect transistor as claimed in claim 1 , wherein
the second conductive-type semiconductor film is fabricated from a polycrystalline semiconductor or amorphous semiconductor.
3. The insulated-gate field effect transistor as claimed in claim 1 , wherein
the semiconductor channel layer is fabricated from a group III-V compound semiconductor.
4. The insulated-gate field effect transistor as claimed in claim 3 , wherein
the gate insulator is made of Ta 2 O 5 .
5. The insulated-gate field effect transistor as claimed in claim 3 , wherein
the gate insulator is made of silicon nitride.