Power device structures and methods using empty space zones
View Patent ↗Power semiconductor devices in which insulated empty space zones are used for field-shaping regions, in place of dielectric bodies previously used. Optionally permanent charge is added at the interface between the insulated empty space zone and an adjacent semiconductor drift region.
1. A semiconductor device, comprising:
at least one current-controlling structure, including a predominantly vertical channel region, and a gate which lies predominantly inside a first trench;
a drift region, into which majority carriers injected from said current-controlling structure flow when said current-controlling structure is in the ON state;
one or more insulated empty space zone-filled regions located within said first trench, in proximity to respective portions of said drift region; and
a drain, into which majority carriers flow from said drift region when said current-controlling structure is in the ON state;
wherein permanent electrostatic charge is located in proximity to sidewalls of said trench, to thereby apply a permanent electric field to said drift region near said trench.
2. The device of claim 1 , wherein said gate lies entirely inside said trench.
3. The device of claim 1 , wherein permanent electrostatic charge is located in proximity to at least one sidewall of said trench, to thereby cause inversion of a layer of said drift region near said sidewall of said trench, and thereby provide an induced drain extension region within said drift region.
4. The device of claim 1 , further comprising a second trench which contains a field plate, but does not contain any gate electrode.
5. The device of claim 1 , wherein said drift region and said drain region have different conductivity types.
6. The device of claim 1 , wherein said drift region is doped p-type, and said majority carriers are electrons.
7. The device of claim 1 , wherein said current-controlling structure comprises a first-conductivity-type source and a second-conductivity type body, and wherein said gate is positioned to controllably invert part of said body to form said channel therein.
8. The device of claim 1 , wherein said drift region and said drain are formed in silicon.
9. A semiconductor device, comprising:
a first-conductivity-type semiconductor source;
a second-conductivity-type semiconductor body region, which separates said source from a semiconductor drift region;
a gate, located in a trench in said body region, which is capacitively coupled to a nearby portion of said body region to control formation of a channel therein; and
an insulated empty space zone region, also located in said trench in proximity to at least part of said drift region;
whereby capacitive coupling to said drift region is reduced by the lower parasitic capacitance of said empty space zone region;
and further comprising permanent electrostatic charges located in proximity to sidewalls of said trench.
10. The device of claim 9 , wherein said gate lies entirely inside said trench.
11. The device of claim 9 , further comprising a second trench which contains a field plate, but does not contain any gate electrode.
12. The device of claim 9 , wherein said drift region and said body region are both doped p-type.
13. A semiconductor device, comprising:
a first-conductivity-type semiconductor source;
a second-conductivity-type semiconductor body region, which vertically separates said source from a semiconductor drift region;
a gate, located in a first part of a trench, which is capacitively coupled to a nearby portion of said body region to control formation of a channel therein;
an insulated empty space zone region, located in a second part of said trench, beneath said gate, in proximity to at least part of said drift region; wherein said second part of said trench is narrower than said first part of said trench;
permanent electrostatic charge in proximity to an interface between said second part of said trench and said drift region; and
a first-conductivity-type drain region below said drift region;
whereby capacitive coupling to said drift region is reduced by the lower parasitic capacitance of said empty space zone region.
14. The device of claim 13 , wherein said permanent electrostatic charge is present in proximity to vertical sidewalls of said second part of said trench, and not in proximity to vertical sidewalls of said first part of said trench.
15. The device of claim 13 , wherein said gate lies entirely inside said first part of said trench.
16. The device of claim 13 , further comprising an additional trench which contains a field plate, but does not contain any gate electrode.
17. The device of claim 13 , wherein said drift region and said drain region have different conductivity types.
18. The device of claim 13 , wherein majority carrier flow passes through said drift region to said drain region in a predominantly vertical direction.