Planar transistor with a relative higher-resistivity base region

Claim 1

AN IMPROVED TRANSISTOR COMPRISING A SEMICONDUCTOR CRYSTAL ELEMENT OF RELATIVELY LOW RESISTIVITY MATERIAL, A LAYER OF SEMICONDUCTOR MATERIAL OF SUBSTANTIALLY UNIFORM THICKNESS ON SAID CRYSTAL ELEMENT HAVING A PLANE SURFACE, A THIN EMITTER REGION OF RELATIVELY LOW RESISTIVITY MATERIAL EXTENDING INTO SAID LAYER FROM SAID PLANE SURFACE AND DEFINING IN SAID LAYER AN EMITTER JUNCTION EXTENDING TO SAID SURFACE AND SURROUNDING SAID EMITTER REGION AT SAID SURFACE, A BASE REGION IN SAID LAYER SURROUNDING SAID EMITTER REGION AT SAID SURFACE AND BOUNDED BY A SMOOTH, REGULAR AND ABRUPT COLLECTOR JUNCTION FORMED, AT THE DEEPEST PART THEREOF, BETWEEN SAID LAYER AND SAID CRYSTAL ELEMENT AND EXTENDING THROUGH SAID LAYER TO SAID PLANE SURFACE, A THIRD REGION EXTENDING FROM SAID SURFACE COMPLETELY THROUGH SAID LAYER AND DEFINING THE PORTION OF SAID COLLECTOR JUNCTION EXTENDING THROUGH SAID LAYER, AND A PROTECTIVE COATING OF INSULATING MATERIAL COMPLETELY COVERING SAID EMITTER AND COLLECTOR JUNCTIONS AT SAID SURFACE, THE MATERIAL IN SAID BASE REGION HAVING A RELATIVELY HIGH RESISTIVITY VALUE FOR INCREASING THE AVALANCHE BREAKDOWN VOLTAGE OF SAID JUNCTIONS, WITH THE LOW RESISTIVITY OF THE MATERIAL IN SAID EMITTER REGION AND THAT IN SAID CRYSTAL ELEMENT DECREASING THE SATURATION VOLTAGE OF THE TRANSISTOR.