Polysilicon doped transistor
AssigneeInternational Business Machines Corporation
InventorsK. Paul Muller, Dominic J. Schepis, Ghavam G. Shahidi
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Abstract
Steep concentration gradients are achieved in semiconductor device of small sizes by using implanted polycrystalline material such as polysilicon as a solid diffusion source. Rapid diffusion of impurities along grain boundaries relative to diffusion rates in monocrystalline materials provides a substantially constant impurity concentration at the interface between polycrystalline material and monocrystalline material. Steepness of the impurity concentration gradient is thus effectively scaled as transistor size is decreased to counter increased short channel and other deleterious effects.
Claims9
A method of forming a semiconductor device including steps of
- forming a recess in a monocrystalline layer adjacent a stud defining a transistor location, depositing polycrystalline material in said recess,
- implanting an impurity in said polycrystalline material, and
- diffusing said impurities along grain boundaries in said polycrystalline material int said monocrystalline material.
A method as recited in claim 6, wherein said implanting and diffusing steps are repeated to form an extension impurity structure adjacent said halo impurity structure.
A semiconductor device including
- sidewalls formed on the interior of an aperture in a polycrystalline semiconductor material and adjacent monocrystalline semiconductor material underlying said aperture
- a gate structure formed within said aperture, and
- an impurity concentration gradient extending below said gate structure.
Dependencies are inferred from the claim text.