Method of forming alignment mark and method of manufacturing semiconductor device

1 . A method of forming an alignment mark for specifying an optimum exposing position, comprising:

preparing a substrate having a semiconductor element and an insulation film covering the semiconductor element;

forming a resist pattern having a first opening on the insulation film, the first opening having a first width which is 1.25 times or less than a second width of a contact plug which is electrically connected to the semiconductor element;

forming a second opening with the first width in the insulation film by etching the insulation film using the resist pattern as a mask;

removing the resist pattern;

forming a first conductive film on the insulation film and inside the second opening by depositing a metal over the insulation film; and

removing the first conductive film on the insulation film while leaving a portion of the first conductive film inside the second opening as an alignment mark.

2 . The method of forming an alignment mark according to claim 1 , further comprising:

forming a third opening in the insulation film by etching the insulation film using the resist pattern as a mask while forming the second opening in the insulation film, the resist pattern further having a fourth opening for forming the third opening, widths of the third and fourth openings being the second width; and

forming a second conductive film inside the fourth opening by depositing a metal over the insulation film while forming the first conductive film on the insulation film and inside the second opening, wherein

the first conductive film on the insulation film is removed while leaving the second conductive film inside the third opening as the contact plug.

3 . The method of forming an alignment mark according to claim 1 , wherein

the shape of the first opening is a line or a framed rectangle.

4 . The method of forming an alignment mark according to claim 1 , wherein

the metal is tungsten.

5 . A method of manufacturing a semiconductor device comprising:

preparing a substrate having a semiconductor element and an insulation film covering the semiconductor element;

forming a resist pattern having a first opening on the insulation film, the first opening having a first width which is 1.25 times or less than the second width of a contact plug which is electrically connected to the semiconductor element;

forming a second opening with the first width in the insulation film by etching the insulation film using the resist pattern as a mask;

removing the resist pattern;

forming a first conductive film on the insulation film and inside the second opening by depositing a metal over the insulating film; and

removing the first conductive film on the insulation film while leaving a portion of the first conductive film inside the second opening as an alignment mark.

6 . The method of manufacturing a semiconductor device according to claim 5 , further comprising:

forming a silicon nitride film over the insulation film.

7 . The method of manufacturing a semiconductor device according to claim 5 , further comprising:

forming a first silicon oxide film on the insulation film;

forming a silicon nitride film on the first silicon oxide film; and

forming a second silicon oxide film on the silicon nitride film.

8 . The method of manufacturing a semiconductor device according to claim 5 , further comprising:

forming a third opening in the insulation film by etching the insulation film using the resist pattern as a mask while forming the second opening in the insulation film, the resist pattern further having a fourth opening for forming the third opening, width of the third and fourth openings being the second width; and

forming a second conductive film inside the fourth opening by depositing a metal over the insulation film while forming the first conductive film on the insulation film and inside the second opening, wherein

the first conductive film on the insulation film is removed while leaving the second conductive film inside the third opening as the contact plug.