Charge Trapping Device
A silicon based semiconductor device and method uses charge trapping to alter a density of carriers available in a channel of a field effect transistor (FET) for conduction. The charge trapping mechanism can be controlled by a source-drain bias voltages applied to the FET, so that the device can be turned off through a control mechanism separate from a gate voltage.
1 . A silicon based semiconductor device comprising:
a silicon based substrate;
a channel region in the silicon based substrate for carrying a device current consisting of charge carriers between a source region and a drain region;
a gate region for receiving a gate bias voltage to control a density of said charge carriers in said channel region available for said device current;
a trapping region located proximate to said channel region, said trapping region being configured for trapping charge carriers and altering said density of charge carriers in said channel region;
wherein said density of charge carriers in said channel region available for said device current is also controllable by a drain bias voltage applied to said drain region, such that said drain bias voltage can reduce said density of charge carriers and turn off the silicon based semiconductor device.
2 . The silicon based semiconductor device of claim 1 , wherein said channel exhibits negative differential resistance.
3 . The silicon based semiconductor device of claim 2 , wherein conduction in said channel can be continuously and dynamically varied between a negative differential resistance mode and a non-negative differential resistance mode.
4 . The silicon based semiconductor device of claim 1 , wherein said trapping region is configured such that said charge carriers are trapped only temporarily and such that a continuous trapping and de-trapping mechanism is set up between said trapping layer and said channel.
5 . The silicon based semiconductor device of claim 1 , wherein a threshold voltage of the silicon based semiconductor device is controlled by said drain bias voltage.
6 . The silicon based semiconductor device of claim I wherein an amount of charge carriers trapped by the charge trapping region is controlled by said drain bias voltage.
7 . A metal-insulator-semiconductor field-effect transistor (MISFET) comprising:
first conductivity type doped source and drain regions formed in the surface of a semiconductor substrate and separated by a second conductivity type doped channel region, said second conductivity type being opposite to said first conductivity;
a gate formed over and electrically insulated from said channel region by a gate dielectric, which gate dielectric includes a charge trapping layer;
said charge trapping layer being located near an interface with said second conductivity type channel region and being configured to trap charge and cause a threshold voltage of the MISFET to be significantly altered in a dynamic and reversible manner in response to an adjustable bias voltage applied to the MISFET;
wherein said adjustable bias voltage is not a program and/or an erase cycle.
8 . The MISFET of claim 7 wherein a negative differential resistance characteristic is achieved by rapid trapping and de-trapping of electrons to and from said charge trapping sites in said charge trapping layer.
9 . The MISFET of claim 7 wherein said charge trapping layer includes charge-trapping sites consisting of one or more islands of metal or semiconductor embedded in said gate dielectric.
10 . The MISFET of claim 7 wherein said charge trapping layer comprises silicon nitride.
11 . The MISFET of claim 7 , wherein said adjustable bias voltage is applied to said first conductivity type source and drain regions.
12 . The MISFET of claim 7 , wherein a trapping mechanism by said charge trapping layer can be selectively disabled by applying a separate bias voltage to a body region portion of the MISFET.