Semiconductor device wherein a property of a first semiconductor layer is different from a property of a second semiconductor layer

Assignee: Semiconductor Energy Laboratory Co., Ltd.

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Quick Facts

Patent No.: US 8,164,095
App. No.: 12/213,036
Granted: Apr 24, 2012
Kind: B2

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Abstract

It is an object to provide a semiconductor device which has a large size and operates at high speed. A top gate transistor which includes a semiconductor layer of single-crystal and a bottom gate transistor which includes a semiconductor layer of amorphous silicon (microcrystalline silicon) are formed over the same substrate. Then, gate electrodes of each transistor are formed with the same layer, and source and drain electrodes are also formed with the same layer. Thus, manufacturing steps are reduced. In other words, two types of transistors can be manufactured by adding only a few steps to the manufacturing process of a bottom gate transistor.

Claims (80)

1. A semiconductor device comprising:

a first semiconductor layer over a substrate;

a first insulating layer over the first semiconductor layer;

a first conductive layer and a second conductive layer over the first insulating layer;

a second insulating layer over the first conductive layer and the second conductive layer;

a second semiconductor layer over the second insulating layer; and

a third conductive layer over the second semiconductor layer,

wherein the first semiconductor layer comprises a single-crystal silicon,

wherein the first conductive layer is overlapped with the first semiconductor layer, and the second conductive layer is overlapped with the second semiconductor layer;

wherein the first semiconductor layer serves as an active layer of a first transistor;

wherein the second semiconductor layer serves as an active layer of a second transistor; and

wherein a property of the first semiconductor layer is different from a property of the second semiconductor layer.

2. The semiconductor device according to claim 1 ,

wherein the first insulating layer serves as a gate insulating layer of the first transistor, and

wherein the first conductive layer serves as a gate electrode of the first transistor.

3. The semiconductor device according to claim 1 ,

wherein the second insulating layer serves as a gate insulating layer of the second transistor, and

wherein the second conductive layer serves as a gate electrode of the second transistor.

4. The semiconductor device according to claim 1 , wherein the third conductive layer is electrically connected to the second semiconductor layer.

5. The semiconductor device according to claim 1 , wherein the second semiconductor layer includes an amorphous semiconductor.

6. The semiconductor device according to claim 1 , wherein the second semiconductor layer includes a microcrystalline semiconductor.

7. A display device, comprising the semiconductor device according to claim 1 and a display element.

8. A liquid crystal display device comprising the semiconductor device according to claim 1 and a display element.

9. An electronic device, comprising the display device according to claim 7 and an operation switch.

10. An electronic device, comprising the liquid crystal display device according to claim 8 and an operation switch.

11. A semiconductor device comprising:

a first semiconductor layer over an insulating substrate;