Logic circuit, light emitting device, semiconductor device, and electronic device
First Claim
1. A logic circuit comprising:
- a depletion-type transistor in which a high power supply potential is applied to one of a source and a drain and a gate is connected to the other of the source and the drain; and
an enhancement-type transistor in which one of a source and a drain is connected to the gate of the depletion-type transistor and a low power supply potential is applied to the other of the source and the drain,wherein the depletion-type transistor and the enhancement-type transistor each comprise;
a first gate electrode;
a gate insulating film over the first gate electrode;
an oxide semiconductor layer over the gate insulating film;
a source electrode and a drain electrode which overlap with edge portions of the first gate electrode and which are in contact with the oxide semiconductor layer;
an oxide insulating film in contact with the oxide semiconductor layer and over a channel formation region; and
a protective insulating layer in contact with the oxide insulating film and over the oxide insulating film,wherein a thickness of the oxide semiconductor layer of the depletion-type transistor is larger than a thickness of the oxide semiconductor layer of the enhancement-type transistor,wherein a first signal is input to the first gate electrode of the enhancement-type transistor,wherein a potential of a portion where the enhancement-type transistor and the depletion-type transistor are connected to each other is output as a second signal, andwherein one of the depletion-type transistor and the enhancement-type transistor comprises a second gate electrode.
1 Assignment
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Accused Products
Abstract
An object is to obtain a desired threshold voltage of a thin film transistor using an oxide semiconductor. Another object is to suppress a change of the threshold voltage over time. Specifically, an object is to apply the thin film transistor to a logic circuit formed using a transistor having a desired threshold voltage. In order to achieve the above object, thin film transistors including oxide semiconductor layers with different thicknesses may be formed over the same substrate, and the thin film transistors whose threshold voltages are controlled by the thicknesses of the oxide semiconductor layers may be used to form a logic circuit. In addition, by using an oxide semiconductor film in contact with an oxide insulating film formed after dehydration or dehydrogenation treatment, a change in threshold voltage over time is suppressed and the reliability of a logic circuit can be improved.
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Citations
24 Claims
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1. A logic circuit comprising:
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a depletion-type transistor in which a high power supply potential is applied to one of a source and a drain and a gate is connected to the other of the source and the drain; and an enhancement-type transistor in which one of a source and a drain is connected to the gate of the depletion-type transistor and a low power supply potential is applied to the other of the source and the drain, wherein the depletion-type transistor and the enhancement-type transistor each comprise; a first gate electrode; a gate insulating film over the first gate electrode; an oxide semiconductor layer over the gate insulating film; a source electrode and a drain electrode which overlap with edge portions of the first gate electrode and which are in contact with the oxide semiconductor layer; an oxide insulating film in contact with the oxide semiconductor layer and over a channel formation region; and a protective insulating layer in contact with the oxide insulating film and over the oxide insulating film, wherein a thickness of the oxide semiconductor layer of the depletion-type transistor is larger than a thickness of the oxide semiconductor layer of the enhancement-type transistor, wherein a first signal is input to the first gate electrode of the enhancement-type transistor, wherein a potential of a portion where the enhancement-type transistor and the depletion-type transistor are connected to each other is output as a second signal, and wherein one of the depletion-type transistor and the enhancement-type transistor comprises a second gate electrode. - View Dependent Claims (2, 3, 4, 5, 6, 14, 15, 16, 17)
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7. A logic circuit comprising:
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a depletion-type transistor in which a high power supply potential is applied to one of a source and a drain and a gate is connected to the other of the source and the drain; and an enhancement-type transistor in which one of a source and a drain is connected to the gate of the depletion-type transistor and a low power supply potential is applied to the other of the source and the drain, wherein the depletion-type transistor and the enhancement-type transistor each comprise; a gate electrode; a gate insulating film over the gate electrode; a source electrode and a drain electrode which overlap with edge portions of the gate electrode and which are provided over the gate insulating film; an oxide semiconductor layer over the gate electrode, the oxide semiconductor layer being over and covering edge portions of the source electrode and the drain electrode; an oxide insulating film in contact with the oxide semiconductor layer and over a channel formation region; and a protective insulating layer in contact with the oxide insulating film and over the oxide insulating film, wherein a thickness of the oxide semiconductor layer of the depletion-type transistor is larger than a thickness of the oxide semiconductor layer of the enhancement-type transistor, wherein a first signal is input to the gate electrode of the enhancement-type transistor, and wherein a potential of a portion where the enhancement-type transistor and the depletion-type transistor are connected to each other is output as a second signal. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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18. A logic circuit comprising:
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a first transistor in which a high power supply potential is applied to one of a source and a drain and a gate is connected to the other of the source and the drain; and a second transistor in which one of a source and a drain is connected to the gate of the first transistor and a low power supply potential is applied to the other of the source and the drain, wherein the first transistor and the second transistor each comprise; a first gate electrode; a gate insulating film over the first gate electrode; an oxide semiconductor layer over the gate insulating film; a source electrode and a drain electrode which overlap with edge portions of the first gate electrode and which are in contact with the oxide semiconductor layer; an oxide insulating film in contact with the oxide semiconductor layer and over a channel formation region; and a protective insulating layer in contact with the oxide insulating film and over the oxide insulating film, wherein a thickness of the oxide semiconductor layer of the first transistor is larger than a thickness of the oxide semiconductor layer of the second transistor, wherein a first signal is input to the first gate electrode of the second transistor, wherein a potential of a portion where the second transistor and the first transistor are connected to each other is output as a second signal, and wherein one of the first transistor and the second transistor comprises a second gate electrode. - View Dependent Claims (19, 20)
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21. A logic circuit comprising:
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a first transistor in which a high power supply potential is applied to one of a source and a drain and a gate is connected to the other of the source and the drain; and a second transistor in which one of a source and a drain is connected to the gate of the first transistor and a low power supply potential is applied to the other of the source and the drain, wherein the first transistor and the second transistor each comprise; a gate electrode; a gate insulating film over the gate electrode; a source electrode and a drain electrode which overlap with edge portions of the gate electrode and which are provided over the gate insulating film; an oxide semiconductor layer over the gate electrode, the oxide semiconductor layer being over and covering edge portions of the source electrode and the drain electrode; an oxide insulating film in contact with the oxide semiconductor layer and over a channel formation region; and a protective insulating layer in contact with the oxide insulating film and over the oxide insulating film, wherein a thickness of the oxide semiconductor layer of the first transistor is larger than a thickness of the oxide semiconductor layer of the second transistor, wherein a first signal is input to the gate electrode of the second transistor, and wherein a potential of a portion where the second transistor and the first transistor are connected to each other is output as a second signal. - View Dependent Claims (22, 23, 24)
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Specification