Si/SiGe vertical junction field effect transistor
AssigneeInternational Business Machines Corporation
InventorsKhalid EzzEldin Ismail, Bernard S. Meyerson
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Abstract
A junction field effect transistor and method for making is described incorporating horizontal semiconductor layers within an opening to form a channel and a semiconductor layer through which the opening was made which forms a gate electrode surrounding the channel. The horizontal semiconductor layers may be a SiGe alloy with graded composition near the source and drain. The invention overcomes the problem of forming low resistance JFET's and provides a gate length that is easily scaleable to submicron dimensions for rf, microwave, millimeter and logic circuits without short channel effects.
Claims25
A junction field effect transistor comprising:
- a first semiconductor layer of a first type;
- a second semiconductor layer of a lightly doped first type formed over said first semiconductor layer,
- a third semiconductor layer of a second type formed over said second semiconductor layer having an opening therein exposing a portion of said second semiconductor layer,
- a layer of dielectric material formed over said third semiconductor layer having an opening therein communicating with said opening in said third semiconductor layer,
- a fourth semiconductor layer of a first type of Si.sub.1-x Ge.sub.x where x increases with thickness formed in said opening of said third semiconductor layer,
- a fifth semiconductor layer of a first type of Si.sub.1-y Ge.sub.y where Y is substantially constant with thickness formed in said opening of said third semiconductor layer, and
- a sixth semiconductor layer of a first type of Si.sub.1-z Ge.sub.z where z decreases with thickness formed in said opening of said layer of dielectric material.
A method for fabricating a junction field effect transistor comprising the steps of:
- forming a first semiconductor layer of a first type;
- forming a second semiconductor layer of a lightly doped first type over said first semiconductor layer,
- forming a third semiconductor layer of a second type over said second semiconductor layer having an opening therein exposing a portion of said second semiconductor layer,
- forming a layer of dielectric material over said third semiconductor layer having an opening therein communicating with said opening in said third semiconductor layer,
- forming a fourth semiconductor layer of a first type of Si.sub.1-x Ge.sub.x where x increases with thickness in said opening of said third semiconductor layer,
- forming a fifth semiconductor layer of a first type of Si.sub.1-y Ge.sub.y where y is substantially constant with thickness in said opening of said third semiconductor layer, and
- forming a sixth semiconductor layer of a first type of Si.sub.1-z Ge.sub.z where z decreases with thickness in said opening of said layer of dielectric material.
Dependencies are inferred from the claim text.