Lateral devices containing permanent charge
View Patent ↗A lateral device includes a gate region connected to a drain region by a drift layer. An insulation region adjoins the drift layer between the gate region and the drain region. Permanent charges are embedded in the insulation region, sufficient to cause inversion in the insulation region.
1. A lateral semiconductor device comprising:
a body region laterally connected to a drain region by a laterally extended semiconductor drift region; and
permanent charge, sufficient to cause depletion in at least a first laterally extended portion of said drift region, at the interface between said drift region and an insulation region;
wherein said drift region also includes a second laterally extended portion having a conductivity type opposite to that of said first portion,
and wherein said first portion overlies said second portion.
2. The lateral semiconductor device of claim 1 , wherein said drift region is formed as a well.
3. The lateral semiconductor device of claim 1 , further comprising a trench gate.
4. The lateral semiconductor device of claim 3 , wherein said trench gate is interposed between said source region and said drain region.
5. The lateral semiconductor device of claim 4 , wherein said trench gate extends laterally above a silicon surface.
6. The lateral semiconductor device of claim 4 , further comprising a gate dielectric surrounding said trench gate, and having a thickness, adjoining said body region, which is less than its thickness adjoining said drift region.
7. The lateral semiconductor device of claim 1 , further comprising an insulation region overlying said drift region between said body region and said drain region; and wherein said permanent charge is embedded within said insulation region.
8. A lateral semiconductor device comprising:
a carrier source;
a laterally extended semiconductor drift region laterally interposed between said carrier source and a drain region; and
permanent charge, embedded in at least one insulating region which vertically adjoins said drift region, which has a polarity opposite to the polarity of ionized dopants in said drift region when said drift region is depleted.
9. The lateral semiconductor device of claim 8 , wherein said carrier source comprises a first-conductivity type source diffusion, and a second-conductivity type channel region which is interposed between said source diffusion and said drift region.
10. The lateral semiconductor device of claim 8 , wherein carrier emission from said carrier source is controlled by voltages applied on a control gate.
11. The lateral semiconductor device of claim 8 , wherein said drift region is formed as a well.
12. The lateral semiconductor device of claim 8 , further comprising a buried region within said drift region.
13. The lateral semiconductor device of claim 8 , further comprising a trench gate.
14. The lateral semiconductor device of claim 13 , wherein said trench gate is between said source region and said drain region.
15. The lateral semiconductor device of claim 13 , wherein said trench gate extends laterally into said insulation region.
16. The lateral semiconductor device of claim 12 , further comprising a second buried region.