Lateral bipolar transistor having electrically induced emitter and collector regions

Claim 1

A lateral bipolar transistor, comprising: a device layer (28) of a semiconductor material doped to a first conductivity type, said device layer having upper and lower major surfaces; a first diffusion region (32) having upper and lower major surfaces, said first diffusion region being doped to a second, opposing conductivity type and formed in said device layer such that at least said upper major surface of the first diffusion region is coincident with the upper major surface of the device layer; a second diffusion region (33) having upper and lower major surfaces, said second diffusion region being doped to said second conductivity type and formed in said device layer with a separation from said first diffusion region, said second diffusion region being formed such that at least said upper major surface of the second diffusion region is coincident with the upper major surface of the device layer; and a base region (31) defined in said device layer between said first and second diffusion regions as a part of the device layer with a separation from at least one of the first and second diffusion regions, said base region having upper and lower major surfaces and formed in said device layer such that said upper major surface of the base region is coincident to the upper major surface of the device layer; characterized in that said bipolar transistor further comprises: an intervening region (32A, 33A) formed in said device layer adjacent to said base region in correspondence to said separation; control gate means (30) provided on the upper major surface of the device layer in correspondence to said intervening region, said control gate means being supplied with a control voltage and inducing an inversion layer (32A, 33A) in the device layer in correspondence to said intervening region as either of emitter and collector regions, so that there occurs a flow of carriers from the first diffusion region to the second diffusion region passing through the base region and the inversion layer.

Claim 13

A method for fabricating a lateral bipolar transistor, characterized by the steps of: forming a first oxide film (68) on an upper major surface of a semiconductor substrate (50); providing a first electrode (53) on said first oxide film in correspondence to one of emitter and collector regions; depositing an oxide layer (74) on said first oxide film (75) to bury the first electrode (53) underneath; applying an anisotropic etching process acting substantially perpendicular to the upper major surface of the device layer to expose the upper major surface of the substrate (50), said anisotropic etching being made to leave a part of said oxide layer (74a) at a side wall of the first electrode (53) in correspondence to a base region (56) of the lateral bipolar transistor; forming a second oxide film (75) to cover the exposed upper major surface of the substrate (50); depositing a conductor layer (76) such that the conductor layer at least covers said oxide layer that is remaining at the side wall of the first electrode; patterning the conductor layer (76) to form a second electrode (76) such that the second electrode covers the second oxide film (75) in correspondence to the other of emitter and collector regions of the lateral bipolar transistor; and implanting impurities into the substrate while using the first and second electrodes (53, 76) as a mask.

Claim 14

A method for fabricating a lateral bipolar transistor, characterized by the steps of: providing an insulation region on an upper major surface of a semiconductor substrate (153) of a first conductivity type in correspondence to a base region of the transistor as a strip-like region (154a) defined by a pair of opposing side walls; covering the upper major surface of the substrate not covered by the strip-like region by a first oxide film (155); depositing a conducting material on an upper major surface of said first oxide film (155) including said strip-like region (154a) such that said strip-like region is buried underneath the conducting material; patterning the conducting material by applying an anisotropic etching process that acts substantially perpendicular to the upper major surface of the substrate (153) to remove the conducting material from the upper major surface of the first oxide film (155) except for the side walls of the strip-like region (154a), said step of patterning including a formation of a bonding pad region (157b) in connection to the part of the conducting material (157a) left at the side walls of the strip-like region (154a); conducting an ion implantation process while using the strip-like region (154a) and the conducting material (157a) left at the side walls of the strip-like region as a mask to form diffusion regions of a second, opposite conductivity type at both sides of the strip-like region as emitter and collector regions.