Lateral double-diffused MOS transistor having deeper drain region than source region

1. A semiconductor power device, comprising:

a first well region having a first conductivity type disposed in a substrate having a second conductivity type opposite the first conductivity type;

a gate overlapping the first well region, and vertically separated from the first well region by an insulating layer;

a source region disposed at a first side of the gate;

a buried layer having the second conductivity type disposed laterally in the first well region, wherein the buried layer is vertically separated from the insulating layer by at least a portion of the first well region;

a drain region having the first conductivity type disposed on a second side of the gate laterally opposite the first side, and contacting the buried layer to form a p-n junction between the drain region and the buried layer;

a body region having the second conductivity type disposed in the substrate at the first side of the gate;

a body contact region contacting the body region; and

a first isolation region disposed between the body contact region and the source region,

wherein the drain region has a depth greater than the source region and is spaced apart from the substrate by the first well region,

wherein the source region is disposed in the body region, the body region having a depth shallower than the drain region.

2. The semiconductor power device of claim 1 , wherein a depth of the drain region is equal to or larger than a depth of the buried layer, and an end of the buried layer contacts the drain region.

3. The semiconductor power device of claim 2 , wherein the drain region has a different doping concentration from that of the source region.

4. The semiconductor power device of claim 1 , further comprising an insulating region disposed between the gate and the drain region.

5. The semiconductor power device of claim 4 , further comprising a doping layer having an opposite conductivity type to the plurality of buried layers.

6. The semiconductor power device of claim 5 , wherein the doping layer is a region having a doping concentration higher than a doping concentration of the first well region.

7. The semiconductor power device of claim 5 , wherein the doping layer has a doping concentration lower than a doping concentration of a first section of the drain region.

8. The semiconductor power device of claim 5 , wherein one end of the doping layer contacts the drain region.

9. The semiconductor power device of claim 5 , wherein the first well and the doping layer are a first conductivity type region, and the buried layer is a second conductivity type region.

10. The semiconductor power device of claim 4 , wherein the insulating region includes one selected from the group consisting of a local oxidation of silicon (LOCOS) oxide layer, a plate-like insulating layer, and a shallow trench isolation (STI) layer.

11. The semiconductor power device of claim 4 , wherein the insulating region is formed by combining a LOCOS oxide layer and an STI layer.

12. The semiconductor power device of claim 4 , wherein the insulating region is a plate-like insulating layer including a LOCOS oxide layer.

13. The semiconductor power device of claim 4 , wherein the insulating region is formed by combining a LOCOS oxide layer, a plate-like insulating layer, and an STI layer.

14. The semiconductor power device of claim 1 , further comprising:

an epitaxial layer disposed on the substrate; and

a third isolation region disposed in the epitaxial layer.

15. The semiconductor power device of claim 1 , wherein the drain region comprises a first portion and a second portion below the first portion, and

wherein the first portion of the drain region has a first dopant concentration profile with respect to depth the same as a dopant concentration profile with respect to depth of the source region.

16. The semiconductor power device of claim 1 , wherein the drain region comprises a first portion and a second portion, and

wherein the first portion has a first dopant concentration profile with respect to depth having a slope greater than a slope of a second dopant concentration profile with respect to depth of the second portion of the drain region.

17. The semiconductor power device of claim 1 , wherein the drain region comprises a first portion and a second portion below the first portion, and

wherein the second portion has a dopant concentration profile with respect to depth that decreases more gradually relative to a dopant concentration profile with respect to depth of the first portion.

18. A semiconductor power device, comprising:

a first well region having a first conductivity type disposed in a substrate having a second conductivity type opposite the first conductivity type;

a gate overlapping the first well region, and vertically separated from the first well region by an insulating layer;

a source region disposed at a first side of the gate;

a buried layer having the second conductivity type disposed laterally in the first well region, wherein the buried layer is vertically separated from the insulating layer by at least a portion of the first well region;

a drain region having the first conductivity type disposed on a second side of the gate laterally opposite the first side, and contacting the buried layer to form a p-n junction between the drain region and the buried layer;

a body region having the second conductivity type disposed in the substrate at the first side of the gate;

a body contact region contacting the body region;

a first isolation region disposed between the body contact region and the source region;

a second isolation region disposed adjacent to the body region; and

a second well region having the second conductivity type disposed below the second isolation region,

wherein the drain region has a depth greater than the source region and is spaced apart from the substrate by the first well region.

19. The semiconductor power device of claim 18 , wherein the second well region has a depth deeper than that of the body region.