What is claimed is:
1. An electric apparatus comprising:
a power supply unit that has terminals to supply power to a circuit board; and
a circuit board that can be mounted to said power supply unit using at least two different mounting orientations and can change the current path depending on the orientation with which it is mounted.
2. An electric apparatus according to claim 1, wherein the power consumed by said circuit board can be changed depending on the direction in which it is mounted to said power supply unit.
3. An electric apparatus according to claim 1, wherein the power consumed by said circuit board can be maintained at a constant level by changing the orientation in which said circuit board is mounted to said power supply unit based on the voltage impressed by said power supply unit to said circuit board.
4. An electric apparatus according to claim 1, wherein said circuit board includes a plurality of connection points at which said circuit board is connected to said power supply unit, and two circuit elements that are installed between the connection points, such that the connection between the two circuit elements may be switched between series connection and parallel connection by changing the orientation in which said circuit board is mounted to said power supply unit.
5. An electric apparatus according to claim 4, wherein said circuit elements include a heating resistor.
6. An electric apparatus according to claim 4, wherein said circuit elements include an electromagnetic induction coil
7. An electric apparatus according to claim 1, wherein said circuit board is mountable to said power supply unit in two different orientations whereby one such orientation has a 180 rotational relationship to the other orientation, such orientation being obtained by rotating the circuit board relative to an axis perpendicular to the surface thereof.
8. An electric apparatus according to claim 1, wherein said circuit board is mountable to said power supply unit in two different orientations whereby one such orientation has a 180 rotational relationship to the other orientation, such orientation being obtained by rotating the circuit board relative to an axis parallel to the surface thereof.
9. A heating device comprising:
a power supply unit that has terminals for supplying power to a circuit board; and
a circuit board that has a heater and that can be mounted to the power supply unit in at least two different orientations such that the current path to the heater can be changed depending on the mounting orientation.
10. A heating device according to claim 9, wherein the output of the heater can be changed depending on the direction in which it is mounted to said power supply unit.
11. A heating device according to claim 9, wherein the output of the heater can be maintained at a constant level by changing the orientation in which said circuit board is mounted to said power supply unit based on the voltage impressed by said power supply unit to said circuit board.
12. A heating device according to claim 9, wherein said heater includes two heating elements, such that the connection between the two heating elements may be switched between series connection and parallel connection by changing the orientation in which said circuit board is mounted to said power supply unit.
13. An image forming apparatus comprising:
an image forming system that forms toner images on recording sheets; and
a fixing device that heats and fuses each toner image formed on a sheet by the image forming system,
wherein the fixing device includes a power supply unit that has terminals for supplying power to a circuit board, and a circuit board that has a heater and that can be mounted to the power supply unit in at least two different orientations such that the current path to the heater can be changed depending on the mounting orientation.
14. An image forming apparatus according to claim 13, wherein the output of the heater can be changed depending on the direction in which it is mounted to said power supply unit.
15. An image forming apparatus according to claim 13, wherein the output of the heater can be maintained at a constant level by changing the orientation in which said circuit board is mounted to said power supply unit based on the voltage impressed by said power supply unit to said circuit board.
16. An image forming apparatus according to claim 13, wherein said heater includes two heating elements, such that the connection between the two heating elements may be switched between series connection and parallel connection by changing the orientation in which said circuit board is mounted to said power supply unit.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of forming a contact on a semiconductor device, comprising;
providing a substrate;
providing a plurality of gate structures defined by a plurality of word lines in a first direction, and a plurality of diffusion regions covered by a first dielectric layer in a second direction over the substrate, wherein the gate structures located underneath the word lines and isolated by the diffusion regions;
forming an etching stop layer, wherein the etching stop layer and the first dielectric layer have different etching selectivity;
forming a second dielectric layer over the substrate; and
forming a plurality of contact holes to the diffusion regions between the word lines by using the etching stop layer as a self-aligned mask.
2. The method of claim 1, wherein the first dielectric layer has a height greater than the gate structures.
3. The method of claim 1, wherein the contact covers a portion of the etching stop layer.
4. The method of claim 1, wherein the material constituting the etching stop layer comprises silicon nitride or silicon oxynitride.
5. The method of claim 1, wherein the material constituting the first dielectric layer comprises silicon oxide.
6. The method of claim 1, wherein after the step of forming the gate structures, further comprises forming a mask strip layer over the gate structures.
7. The method of claim 6, wherein the step of forming the first dielectric layer comprises:
forming a dielectric material layer over the substrate;
removing a portion of the dielectric material layer above the mask strip layer until a portion of the mask strip layer is exposed and the dielectric material layer between the gate structures is retained; and
removing the mask strip layer.
8. The method of claim 7, wherein the step of forming the dielectric material layer comprises performing a high-density plasma chemical vapor deposition (HDPCVD) process.
9. The method of claim 7, wherein the step of removing a portion of the dielectric material layer comprises etching with hot phosphoric acid until the top corners of the mask strip layer are exposed.
10. The method of claim 1, wherein the step of forming the etching stop layer comprises:
forming an etching stop material layer over the substrate to cover the word lines and the dielectric strips and fill openings between the word lines; and
performing an anisotropic etching operation to remove a portion of the etching stop material layer.
11. The method of claim 1, wherein each of the gate structures comprises a bottom dielectric layer, a charge storage layer and a top dielectric layer.
12. The method of claim 11, wherein the bottom dielectric layer comprises a tunneling layer, the charge storage layer comprises a charge trapping layer, and the top dielectric layer comprises a charge barrier layer.
13. The method of claim 11, wherein the bottom dielectric layer comprises a tunneling layer, the charge storage layer comprises a floating gate layer, and the top dielectric layer comprises an inter-gate dielectric layer.