Method of manufacturing semiconductor apparatus
A method of manufacturing a semiconductor apparatus includes forming a trench in a semiconductor layer, forming a gate electrode inside the trench, forming a thermally-oxidized film on the gate electrode inside the trench, forming a silicate glass film on the thermally-oxidized film inside the trench, forming a body region inside the semiconductor layer, and forming a source region on the body region. The method provides a semiconductor apparatus having reduced fluctuation of a channel length and low ON-resistance.
1. A method of manufacturing a vertical MOSFET, said method comprising:
forming a trench in a semiconductor layer of a first conductivity type;
forming a gate electrode inside the trench;
forming a first insulating film on the gate electrode inside the trench;
forming a second insulating film on the first insulating film inside the trench;
forming a body region of a second conductivity type opposite to the first conductivity type inside the semiconductor layer after forming the second insulating film; and
forming a source region of the first conductivity type in an upper portion of the body region.
2. The method of manufacturing a vertical MOSFET according to claim 1 , wherein when the second insulating film is formed inside the trench, the second insulating film is formed on the semiconductor layer, then the second insulating film is etched back to expose the semiconductor layer and leave the second insulating film in the trench.
3. The method of manufacturing a vertical MOSFET according to claim 2 , wherein an exposed surface of the semiconductor layer and a surface of the second insulating film left in the trench form substantially a coplanar surface.
4. The method of manufacturing a vertical MOSFET according to claim 1 , wherein a gate insulating film is formed between an inner surface of the trench and the gate electrode.
5. The method of manufacturing a vertical MOSFET according to claim 4 , wherein the first insulating film has a thickness which is greater than a thickness of the gate insulating film.
6. The method of manufacturing a vertical MOSFET according to claim 1 , wherein the gate electrode comprises polysilicon.
7. The method of manufacturing a vertical MOSFET according to claim 6 , wherein the first insulating film comprises a thermally-oxidized film of the polysilicon in the gate electrode.
8. The method of manufacturing a vertical MOSFET according to claim 1 , wherein the second insulating film comprises at least one of BPSG (Boron doped Phospho-Silicate Glass) and NSG (Non-doped Silicate Glass).
9. The method of manufacturing a vertical MOSFET according to claim 1 , further comprising:
forming a body contact region of the second conductivity type adjacent to the source region, an impurity concentration of the body contact region being higher than that of the body region.
10. The method of manufacturing a vertical MOSFET according to claim 9 , wherein the trench comprises a plurality of elongated portions arranged in parallel to each other in a plan view.
11. The method of manufacturing a vertical MOSFET according to claim 10 , further comprising:
forming another source region,
wherein the source region, the body contact region and the another source region are arranged in this order in a longitudinal direction of the elongated portion of the trench such that the source region, the body contact region and the another source region are sandwiched between adjacent elongated portions of the trench.
12. The method of manufacturing a vertical MOSFET according to claim 1 , wherein the semiconductor layer comprises an epitaxial layer formed on a semiconductor substrate of the first conductivity type.
13. The method of manufacturing a vertical MOSFET according to claim 12 , wherein the semiconductor layer and the semiconductor substrate function as a drain region of the vertical MOSFET.
14. The method of manufacturing a vertical MOSFET according to claim 13 , further comprising:
forming a source electrode on a surface of the source region and the second insulating film; and
forming a drain electrode on a back surface of the semiconductor substrate.
15. The method of manufacturing a vertical MOSFET according to claim 1 , wherein the first insulating film is in contact with the source region.
16. The method of manufacturing a vertical MOSFET according to claim 1 , wherein the second insulating film is embedded in the first insulating film.
17. The method of manufacturing a vertical MOSFET according to claim 1 , wherein an exposed surface of the semiconductor layer, an upper surface of the second insulating film, and an upper surface of the first insulating film are coplanar.
18. The method of manufacturing a vertical MOSFET according to claim 1 , wherein an upper surface of the second insulating film is coplanar with an upper surface of the trench.
19. A method of forming a semiconductor device according to claim 1 , wherein the second conductivity type is opposite to the first conductivity type.
20. A method of forming a semiconductor device, said method comprising:
forming a trench in a semiconductor layer of a first conductivity type;
forming a gate electrode inside the trench;
forming a first insulating film on the gate electrode inside the trench;
forming a second insulating film on the first insulating film inside the trench;
forming a body region of a second conductivity type inside the semiconductor layer after forming the second insulating film; and
forming a source region of the first conductivity type in an upper portion of the body region.