Insulated gate field-effect transistor

Claim 1

An insulated gate field-effect transistor having a threshold voltage adjustable within a limited range, comprising: a substrate; a source area formed in said substrate; a drain area formed in said substrate and spaced from said source area to define a channel region therebetween; a gate electrode disposed over said channel region; an intermediate gate electrode disposed between the gate electrode and channel region; a control part galvanically connected to the intermediate gate electrode and extending from between the channel region and gate electrode; a first pair of partial layers of gate dielectric disposed between the intermediate gate electrode and the channel region and between the intermediate gate electrode and the gate electrode; a second pair of partial layers of dielectric embedding the control part, the first and second pair of partial layers having sufficient thickness so that no charges, during operation, can flow to either said intermediate gate electrode or said control part; and an auxiliary electrode capacitively coupled to said control part, whereby the d.c. voltage potential of both said control part and said intermediate gate electrode is floating in the absence of a voltage applied to the auxiliary electrode with respect to the substrate and the threshold voltage may be adjusted by the application of a voltage to the auxiliary electrode.