Semiconductor devices with graded dopant regions

Abstract

Most semiconductor devices manufactured today, have uniform dopant concentration, either in the lateral or vertical device active (and isolation) regions. By grading the dopant concentration, the performance in various semiconductor devices can be significantly improved. Performance improvements can be obtained in application specific areas like increase in frequency of operation for digital logic, various power MOSFET and IGBT ICS, improvement in refresh time for DRAM's, decrease in programming time for nonvolatile memory, better visual quality including pixel resolution and color sensitivity for imaging ICs, better sensitivity for varactors in tunable filters, higher drive capabilities for JFET's, and a host of other applications.

1 - 8 . (canceled) 
     
     
         9 . A semiconductor device comprising:
 a surface layer;   a substrate;   an active region including at least one emitter, at least one base and at least one collector disposed in the above said device;   at least one drift layer positioned between said emitter and said collector, said drift layer having at least one graded concentration of dopants, said drift layer further having a first static unidirectional electric field to aid movement of carriers from said emitter to said collector; and   at least one isolation region disposed in the semiconductor device, said isolation region having a graded concentration of dopants and a second static unidirectional electric field to aid isolation between active regions.   
     
     
         10 . The semiconductor device of  claim 9  wherein said static unidirectional electric fields are adapted to respective grading of dopants to aid movements of carriers in respective active regions. 
     
     
         11 . A semiconductor device comprising:
 at least one active region with a channel conduction surface;   at least one active device with a vertical conduction;   a first static unidirectional electric field in said channel conducting region; said first unidirectional electric field having a graded dopant concentration;   a second static unidirectional electric field in said vertical conduction; said second static unidirectional electric field having a graded dopant concentration; and   a third static unidirectional electric field; said third static unidirectional electric field having a graded dopant concentration.   
     
     
         12 . The semiconductor device of  claim 9  wherein the semiconductor device is a silicon substrate. 
     
     
         13 . The semiconductor device of  claim 9  wherein the semiconductor device is an III-V compound substrate. 
     
     
         14 . The semiconductor device of  claim 9  wherein the semiconductor device is an II-VI compound substrate. 
     
     
         15 . The semiconductor device of  claim 9  wherein the semiconductor device is an organic material substrate. 
     
     
         16 . The semiconductor device of  claim 9  wherein the semiconductor device is a silicon carbide substrate. 
     
     
         17 . The semiconductor device of  claim 9  wherein the semiconductor device has at least one bipolar transistor. 
     
     
         18 . The semiconductor device of  claim 9  wherein the semiconductor device has at least one vertical bipolar transistor. 
     
     
         19 . The semiconductor device of  claim 9  wherein the semiconductor device has at least one planar bipolar transistor with a conducting surface layer. 
     
     
         20 . The semiconductor device of  claim 9  wherein the semiconductor device has at least one MOS transistor. 
     
     
         21 . The semiconductor device of  claim 9  wherein the semiconductor device has at least one IGBT. 
     
     
         22 . A semiconductor device comprising:
 a substrate;   a surface layer;   an active region including at least one emitter and one collector disposed in the device;   a single drift layer disposed between said emitter and said collector, said drift layer having at least one graded concentration of dopants, said drift layer further having a first static unidirectional electric field to aid movement of carriers from said emitter to said collector; and   at least one isolation region disposed in the semiconductor device, said isolation region having a graded concentration of dopants and a second static unidirectional electric field to aid movement of carriers.   
     
     
         23 . The semiconductor device of  claim 22  wherein the semiconductor device is a varactor. 
     
     
         24 . The semiconductor device of  claim 22  wherein the semiconductor device is a varistor. 
     
     
         25 . The semiconductor device of  claim 22  wherein the semiconductor device is an avalanche transistor. 
     
     
         26 . The semiconductor device of  claim 22  wherein the semiconductor device is a Zener diode. 
     
     
         27 . The semiconductor device of  claim 22  wherein the semiconductor device is a Schottky diode. 
     
     
         28 . The semiconductor device of  claim 22  wherein the semiconductor device is a tunneling diode. 
     
     
         29 . The semiconductor device of  claim 22  wherein the semiconductor device is an Esaki diode.