Bipolar transistor and a method of manufacturing the same

Abstract

A bipolar transistor having the enhanced characteristics is fabricated by etching a base mesa, which is formed below an emitter mesa (upper emitter layer) and a base electrode, to have jut regions on the edges of its generally rectangular region. A mask film, e.g., insulating film, is formed to cover the rectangular region and jut regions, and the base layer is etched by use of the insulating film for masking thereby to form a base mesa. Consequently, abnormal etching can be prevented from occurring along the base electrode and emitter mesa on the edges of the area where the base electrode and emitter mesa confront, and the increase of resistance between the base layer and the emitter layer can be prevented, whereby the bipolar transistor can have the enhanced characteristics.

1 . A bipolar transistor including a collector, a base and an emitter, said transistor comprising: 
 (a) a base mesa including said base and formed over said collector;    (b) an emitter mesa including said emitter and formed over said base mesa and extending in a first direction; and    (c) a base electrode formed over said base mesa,    (d) said base mesa including a jut region in the first direction of extension of said emitter mesa.    
   
   
       2 . A bipolar transistor according to  claim 1 , 
 wherein said base electrode has a first side which confronts a second side of said emitter mesa, and    wherein there is a distance, which is larger than or equal to the height of said base mesa plus 0.3 μm, between the second side, at its end immediate to said jut region, and an edge of said jut region.