Semiconductor device and method for fabricating the same

1. A method for fabricating a semiconductor device, comprising:

forming a spin orbit torque (SOT) layer on a substrate;

forming a magnetic tunneling junction (MTJ) on and directly contacting the SOT layer;

forming a cap layer on and directly contacting the SOT layer and the MTJ;

performing an etching process to remove part of the cap layer so that the cap layer directly on the SOT layer and the cap layer on sidewalls of the MTJ comprise different thicknesses; and

patterning the cap layer and the SOT layer at the same time.

2. The method of claim 1 , wherein the substrate comprises a magnetic random access memory (MRAM) region and a logic region, the method comprising:

forming a first inter-metal dielectric (IMD) layer on the substrate;

forming a first metal interconnection and a second metal interconnection in the first IMD layer on the MRAM region;

forming the SOT layer on the first metal interconnection and the second metal interconnection;

forming a MTJ stack on the SOT layer;

forming a hard mask on the MTJ stack;

using the hard mask to pattern the MTJ stack for forming the MTJ;

forming the cap layer on the SOT layer and the hard mask; and

patterning the cap layer and the SOT layer.

3. The method of claim 2 , further comprising performing the etching process to remove a portion of the cap layer before patterning the cap layer and the SOT layer.

4. The method of claim 2 , further comprising:

forming a second IMD layer around the cap layer; and

forming a third metal interconnection on the logic region.

5. The method of claim 4 , wherein a top surface of the cap layer is lower than a top surface of the third metal interconnection.

6. The method of claim 4 , further comprising:

forming a stop layer on the second IMD layer;

forming a third IMD layer on the stop layer;

forming a fourth metal interconnection on the MRAM region to connect to the SOT layer; and

forming a fifth metal interconnection on the logic region to connect to the third metal interconnection.

7. The method of claim 2 , wherein a first portion of the cap layer on the first IMD layer and a second portion of the cap layer adjacent to the MTJ comprise different thicknesses.

8. The method of claim 2 , wherein a thickness of the first portion of the cap layer on the first IMD layer is less than a thickness of the second portion of the cap layer adjacent to the MTJ.

9. The method of claim 1 , wherein a sidewall of the cap layer is aligned with a sidewall of the SOT layer.

10. A semiconductor device, comprising:

a spin orbit torque (SOT) layer on a substrate;

a magnetic tunneling junction (MTJ) on the SOT layer;

a hard mask on the MTJ; and

a cap layer on and directly contacting the SOT layer and the hard mask, wherein the cap layer directly on the SOT layer and the cap layer on sidewalls of the MTJ comprise different thicknesses.

11. The semiconductor device of claim 10 , wherein the substrate comprises a magnetic random access memory (MRAM) region and a logic region, the semiconductor device comprising:

a first inter-metal dielectric (IMD) layer on the substrate;

a first metal interconnection and a second metal interconnection in the first IMD layer on the MRAM region;

the SOT layer on the first metal interconnection and the second metal interconnection;

the MTJ on the SOT layer;

the hard mask on the MTJ;

a second IMD layer around the MTJ; and

a third metal interconnection in the second IMD layer on the logic region.

12. The semiconductor device of claim 11 , further comprising:

a stop layer on the second IMD layer;

a third IMD layer on the stop layer;

a fourth metal interconnection on the MRAM region to connect to the SOT layer; and

a fifth metal interconnection on the logic region to connect to the third metal interconnection.

13. The semiconductor device of claim 11 , wherein a top surface of the cap layer is lower than a top surface of the third metal interconnection.

14. The semiconductor device of claim 11 , wherein a first portion of the cap layer on the first IMD layer and a second portion of the cap layer adjacent to the MTJ comprise different thicknesses.

15. The semiconductor device of claim 11 , wherein a thickness of the first portion of the cap layer on the first IMD layer is less than a thickness of the second portion of the cap layer adjacent to the MTJ.

16. The semiconductor device of claim 10 , wherein a sidewall of the cap layer is aligned with a sidewall of the SOT layer.