Semiconductor device and manufacturing method for semiconductor device
View Patent ↗To provide a semiconductor device capable of reducing a gate capacitance, and preventing breakdown of a gate oxide film if a large amount of current flows. A semiconductor device according to an embodiment of the present invention includes: an epitaxial layer; a channel region formed on the epitaxial layer; a trench extending from a surface of the channel region to the epitaxial layer; a gate oxide film that covers an inner surface of the trench; a gate electrode filled into the trench; and a buried insulating film formed below the gate electrode and away from the gate oxide film.
1. A semiconductor device, comprising:
a first semiconductor layer of a first conductivity type;
a channel formation region of a second conductivity type formed in the first semiconductor layer;
a trench extending from a surface of the channel formation region to the first semiconductor layer;
a gate insulating film formed on an inner surface of the trench;
a gate electrode formed in the trench, the gate electrode having a bottom surface; and
a buried insulating film formed below the bottom surface of the gate electrode apart from the gate insulating film,
wherein the buried insulating film is buried within the first semiconductor layer in an area beneath the trench excluding an area beneath the channel formation region.
2. The semiconductor device according to claim 1 , wherein the buried insulating film has a dielectric constant smaller than a dielectric constant of the first semiconductor layer.
3. The semiconductor device according to claim 1 , wherein the buried insulating film covers a bottom surface of the gate electrode.
4. The semiconductor device according to claim 1 , wherein the buried insulating film has substantially the same shape as the gate insulating film covering a bottom surface of the trench.
5. The semiconductor device according to claim 1 , wherein an end of the buried insulating film is an extension of the gate insulating film that covers side surfaces of the trench.
6. The semiconductor device according to claim 1 , wherein the buried insulating film includes a plurality of insulating films that are formed separately and spaced apart from one another.
7. The semiconductor device according to claim 1 , wherein the first semiconductor layer includes a semiconductor substrate and an epitaxial layer formed on the semiconductor substrate, and
the plurality of buried insulating films are buried in the epitaxial layer.
8. The semiconductor device according to claim 1 , further comprising:
a source diffusion region of the first conductivity type formed in the channel formation region; and
a backgate diffusion region of the second conductivity type formed in the channel diffusion region, the backgate diffusion region having higher impurity concentration than that of the channel diffusion region.
9. The semiconductor device according to claim 1 , wherein the first semiconductor layer includes a semiconductor substrate and an epitaxial layer formed on the semiconductor substrate, and
the buried insulating film is buried in the semiconductor substrate.
10. The semiconductor device according to claim 1 , wherein the first semiconductor layer includes a semiconductor substrate and an epitaxial layer formed on the semiconductor substrate, and
the buried insulating film is buried in at least one of the semiconductor substrate and the epitaxial layer.
11. The semiconductor device according to claim 1 , wherein each of the plurality of insulating films is formed entirely below the bottom surface of each gate electrode.
12. The semiconductor device according to claim 1 , wherein the buried insulating film is completely surrounded by the first semiconductor layer.