Ion-implanted depletion-mode IGFET

P-channel IGFET\´s have been ion-implanted with boron to produce a Gaussian dopant profile which is almost entirely in the silicon. These IGFET\´s exhibit depletion mode device behavior due to a subsurface built-in channel, and they have more reproducible conductance characteristics than those fabricated by leading edge implants for which only simple shifts of threshold voltage occur. The built-in subsurface channel structure results in a device which is characterized by both a flatband (VFB) and a drain saturation voltage (VDSAT) rather than a threshold voltage. The fabrication process users 120 keV boron ions implanted through an Al2O3(500Å)-Sio2(1000Å) gate dielectric into Si at an angle of 7° from the axis. Typical device parameters for an ion dosage of /cm²are volt, volt at . For W/L = 1, µmhos at and volt.