Double diffused mos field-effect-transistor and process for its manufacture

Claim 1

Method for forming diffused metal-oxide silicon field-effect transistors with predictable transconductance, characterized by the following steps : forming first (52) and second (54) regions of a first conductivity type, separated by a first distance on a substrate (32) of the first conductivity type ; forming first and second regions (62, 66) of a second conductivity type within said first and second regions of said first conductivity type, and forming a third region (64) of the second conductivity type between said first and second regions (52, 54) of said first conductivity type with a second distance from the first region of the first conductivity type, and a third distance from the second region of the first conductivity type, for a common drain region of two field-effect transistors, the first and second regions of the second conductivity type serving as the respective source regions of the two FET ; implanting of ions of the second conductivity type into a layer (74) of the substrate (32) lying over the third region (64) of the second conductivity type, the layer (74) extending on both sides into the region separating the third region (64) of the second conductivity type from the neighbouring first and second regions (52, 54) of the first conductivity type, whereby a parallel-connected pair of field-effect transistors is formed in which the transconductance of the first FET compensates the deviation of the transconductance of the second transistor caused by the misalignment of the predetermined opening of the implantation mask.