Method of making enhancement-mode and depletion-mode IGFETS with

Details Method of making enhancement-mode and depletion-mode IGFETS with Method of making enhancement-mode and depletion-mode IGFETS with

1997-04-21

1999-07-13

Tsai, Jey

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

438291, H01L 21336

Patent

active

059239840

ABSTRACT:
A method of making enhancement-mode and depletion-mode IGFETs with different gate materials is disclosed. The method includes providing a semiconductor substrate with first and second device regions, forming a first gate composed of a first gate material over the first device region, forming a second gate composed of a second gate material over the second device region, implanting a dopant into the substrate and into the first and second gates to implant source and drain regions in the first device region and source and drain regions in the second device region, and transferring the dopant through the first gate into a first channel region in the first device region beneath the first gate without transferring essentially any of the dopant through the second gate into a second channel region in the second device region beneath the second gate, thereby providing depletion-mode doping in the first channel region while retaining enhancement-mode doping in the second channel region. The dopant can be implanted through the first gate into the first channel region. Alternatively, the dopant can be implanted into the first gate but not the first channel region and then diffused from the first gate into the first channel region. Advantageously, by employing different gate materials, a single implant step can be used to provide lightly doped source/drain regions for enhancement and depletion-mode IGFETs as well as depletion-mode doping for channel regions of depletion-mode IGFETs (with gates composed of the first gate material) while retaining enhancement-mode doping for channel regions of enhancement-mode IGFETs (with gates composed of the second gate material).

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