Semiconductor device and method of manufacturing the same semiconductor device

1. A semiconductor device, comprising: a semiconductor layer in which a via hole penetrating an upper surface of the semiconductor layer to a lower surface of the semiconductor layer is provided;

a first insulating film provided over the lower surface of the semiconductor layer and an inner surface of the via hole;

a second insulating film provided over the lower surface of the semiconductor layer and the inner surface of the via hole with the first insulating film interposed between the second insulating film and the semiconductor layer;

a device layer including a semiconductor element and provided on a side of the upper surface of the semiconductor layer;

a lower electrode that is provided in the via hole with the first and second insulating films interposed between the lower electrode and the inner surface of the via hole and is electrically connected to the device layer;

a protective insulating film that is provided on the upper surface of the semiconductor layer with the device layer interposed therebetween and protects the device layer; and

an upper electrode that is provided to be opposed to the lower electrode with the device layer interposed therebetween and is electrically connected to the device layer,

wherein the first insulating film has a greater thickness over the lower surface of the semiconductor layer than over the inner surface of the via hole in the semiconductor layer, wherein the second insulating film has a greater thickness over the lower surface of the semiconductor layer than over the inner surface of the via hole in the semiconductor layer, and

wherein a step coverage of the first insulating film and a step coverage of the second insulating film are not equal to each other.

2. The semiconductor device according to claim 1 , wherein one of the first insulating film and the second insulating film has a greater coefficient of linear expansion than the semiconductor layer, and another of the first insulating film and the second insulating film has a smaller coefficient of linear expansion than the semiconductor layer.

3. The semiconductor device according to claim 2 , wherein the first insulating film has a smaller coefficient of linear expansion than the semiconductor layer, and the second insulating film has a greater coefficient of linear expansion than the semiconductor layer.

4. The semiconductor device according to claim 2 , wherein the one of the first insulating film and the second insulating film that has a greater coefficient of linear expansion than the semiconductor layer is a Low-k film.

5. The semiconductor device according to claim 3 , wherein the second insulating film that has a greater coefficient of linear expansion than the semiconductor layer is a Low-k film.

6. The semiconductor device according to claim 1 , wherein the semiconductor layer is a silicon layer.

7. The semiconductor device according to claim 2 , wherein the semiconductor layer is a silicon layer.

8. The semiconductor device according to claim 3 , wherein the semiconductor layer is a silicon layer.

9. The semiconductor device according to claim 2 , wherein the one of the first insulating film and the second insulating film that has a greater coefficient of linear expansion than the semiconductor layer has a lower step coverage than the another of the first insulating film and the second insulating film.

10. The semiconductor device according to claim 7 , wherein the one of the first insulating film and the second insulating film that has a greater coefficient of linear expansion than the semiconductor layer has a lower step coverage than the another of the first insulating film and the second insulating film.

11. The semiconductor device according to claim 1 , wherein the first insulating film and the second insulating film extend integrally from a side wall of the via hole to the lower surface of the semiconductor layer.