HIGH THRESHOLD VOLTAGE NMOS TRANSISTORS FOR LOW POWER IC TECHNOLOGY
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Accused Products
Abstract
Transistors exhibiting different electrical characteristics such as different switching threshold voltage or different leakage characteristics are formed on the same chip or wafer by selectively removing a film or layer which can serve as an out-diffusion sink for an impurity region such as a halo implant and out-diffusing an impurity such as boron into the out-diffusion sink, leaving the impurity region substantially intact where the out-diffusion sink has been removed. In forming CMOS integrated circuits, such a process allows substantially optimal design for both low-leakage and low threshold transistors and allows a mask and additional associated processes to be eliminated, particularly where a tensile film is employed to increase electron mobility since the tensile film can be removed from selected NMOS transistors concurrently with removal of the tensile film from PMOS transistors.
2 Citations
19 Claims
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1-11. -11. (canceled)
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12. A method of making an semiconductor device having transistors of a first conductivity type but exhibiting different electrical characteristics, said method comprising steps of
forming transistors of a first conductivity type having an impurity region containing an impurity which increases a voltage threshold of said transistors of said first conductivity type, forming a blanket film covering said transistors of said first conductivity type, removing a portion of said blanket film from at least one selected transistor, and out-diffusing an impurity from said impurity region of transistors of said first conductivity type to remaining portions of said blanket film whereby a voltage threshold of transistors of said first conductivity type other than said at least one selected transistor is reduced.
Specification