Semiconductor device and method for manufacturing the same

1. A semiconductor device comprising:

a first barrier layer having a barrier property against oxygen and hydrogen over a substrate;

a first insulator over the first barrier layer;

a second insulator over the first insulator;

a third insulator over the second insulator;

a transistor including an oxide semiconductor over the third insulator;

a fourth insulator including an oxygen-excess region over the transistor; and

a second barrier layer having a barrier property against oxygen and hydrogen over the fourth insulator,

wherein the transistor comprises a first conductor with oxidation resistance, a second conductor with oxidation resistance, and a third conductor with oxidation resistance,

wherein the second insulator comprises a high-k material,

wherein the first barrier layer and the second barrier layer are in contact with each other in an outer edge of a region where the transistor is provided, and

wherein the transistor is surrounded by the first barrier layer and the second barrier layer.

2. The semiconductor device according to claim 1 , wherein the first conductor, the second conductor, and the third conductor are each tantalum nitride.

3. The semiconductor device according to claim 1 ,

wherein the first barrier layer and the second barrier layer are each silicon nitride, and

wherein an amount of hydrogen that is released from the silicon nitride and is converted into hydrogen atoms is less than or equal to 10×10 15 atoms/cm 2 , preferably less than or equal to 5×10 15 atoms/cm 2 when measured by TDS analysis at a temperature range from 50° C. to 500° C.

4. The semiconductor device according to claim 1 , wherein the first barrier layer and the second barrier layer are each aluminum oxide.

5. The semiconductor device according to claim 1 ,

wherein the first barrier layer is aluminum oxide,

wherein the second barrier layer has a stacked-layer structure including silicon nitride, and

wherein an amount of hydrogen that is released from the silicon nitride and is converted into hydrogen atoms is less than or equal to 10×10 15 atoms/cm 2 , preferably less than or equal to 5×10 15 atoms/cm 2 when measured by TDS analysis at a temperature range from 50° C. to 500° C.

6. A method for manufacturing a semiconductor device, comprising the steps of:

forming a first barrier layer having a barrier property against oxygen and hydrogen over a substrate;

forming a first conductor over the first barrier layer;

forming a first insulator over the first conductor;

forming a second insulator comprising a high-k material over the first insulator;

forming a third insulator over the second insulator;

forming a first oxide semiconductor over the third insulator;

forming a second conductor with oxidation resistance over the first oxide semiconductor;

processing the second conductor into an island shape;

processing the first oxide semiconductor and the third insulator into an island shape with the use of the island-shaped second conductor as a mask;

performing heat treatment;

processing the island-shaped second conductor to form a third conductor and a fourth conductor;

forming a second oxide semiconductor over the first oxide semiconductor, the third conductor, and the fourth conductor;

forming a fourth insulator over the second oxide semiconductor;

forming a fifth conductor with oxidation resistance that has an island shape over the fourth insulator;

forming a fifth insulator over the fourth insulator and the fifth conductor;

forming an opening in the fifth insulator so that the opening reaches the third conductor, the fourth conductor, and the fifth conductor;

forming a sixth conductor in the opening;

forming a second barrier layer having a barrier property against oxygen and hydrogen over the sixth conductor;

performing oxygen plasma treatment on the second barrier layer and the fifth insulator; and

forming a third barrier layer having a barrier property against oxygen and hydrogen over the second barrier layer and the fifth insulator.

7. The method for manufacturing a semiconductor device, according to claim 6 , wherein the first barrier layer and the third barrier layer are each formed by a sputtering method.

8. The method for manufacturing a semiconductor device, according to claim 6 , wherein the fifth conductor has a stacked-layer structure including tantalum nitride formed by an ALD method and tantalum nitride formed by a sputtering method.