Near-intrinsic thin-film SOI FETS
AssigneeMassachusetts Institute of Technology
InventorChun-Teh Lee
Life of this patent
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Abstract
A submicrometer, near-intrinsic, thin-film, SOI complementary filed effect transistor structure is disclosed. The device is characterized by having a gate comprising material having a work function which approximates its Fermi level to the middle of the band gap of the channel material. Such devices display desirable transconductance, subthreshold slope and punch-through resistance.
Claims40
A field effect transistor device which comprises:
- a) an insulating layer;
- b) a substantially single crystal semiconducting film upon said insulating layer, said semiconducting film having a thickness of less than about 0.5 um in regions defining device channels, the film in said channel regions having a doping concentration of less than about 10.sup.16 cm.sup.-3, said film further defining source and drain regions having an impurity concentration higher than that of the channel regions;
- c) a gate dielectric upon the channel regions;
- and,
- d) a gate material upon the gate dielectric, said gate material having a work function such that the gate material has a Fermi level that is positioned at about the middle of the bandgap of the semiconducting film of the channel regions.
A field effect transistor device which comprises:
- a) a silicon substrate;
- b) an oxide layer upon the substrate;
- c) a substantially single crystal silicon film upon the oxide layer, said silicon film having a thickness of less than about 0.5 um in areas defining device channel regions, the film in said channel regions having a doping concentration of less than about 10.sup.16 cm.sup.-3, said film further defining source and drain regions having an impurity concentration higher than that of the channel regions;
- d) a gate oxide upon the channel regions;
- and
- e) a gate material upon the gate oxide and positioned over the channel regions, said gate material having a work function of between about 4.4 and about 5.0 eV such that the gate material has a Fermi level positioned at about the middle of the bandgap of the silicon channel region.
In a near intrinsic, thin-film, semiconductor-on-insulator, field effect transistor characterized by having a substrate, a buried insulating layer, a near-intrinsic semiconductor film layer having a doping concentration of less than about 10.sup.16 cm.sup.31 3, a gate material upon a gate dielectric extending over the layer, the layer being patterned to define source, drain and channel regions;
- the improvement which comprises, as the gate material, a material having a work function which approximates its Fermi level to the middle of the bandgap of the semiconductor film material wherein the film comprises a single crystal epitaxial layer.
A complementary insulated gate field effect transistor circuit having both n-type and p-type transistors in which each transistor comprises:
- a) an insulating layer;
- b) a single crystal semiconducting film upon said insulating layer, said semiconducting film having a thickness of less than about 0.5 um in regions defining device channels, the film in said channel regions having a doping concentration of less than about 10.sup.16 cm.sup.31 3, said film further defining source and drain regions having an impurity concentration higher than that of the channel regions;
- c) a gate dielectric upon the channel regions;
- and
- d) a gate material upon the gate dielectric, the same gate material extending over the channel regions in both n-type and p-type transistors of the circuit, said gate material having a work function which approximates its Fermi level to the middle of the bandgap of the channel semiconductor material.
Dependencies are inferred from the claim text.