Thyristor-based semiconductor memory device with back-gate bias
View Patent ↗In accordance with an embodiment of the present invention, a thyristor-based semiconductor memory device may comprise an array of thyristor-based memory formed in an SOI wafer. A supporting substrate may be formed with a density of dopants sufficient to assist delivery of a bias level to the backside of an insulating layer beneath a thyristor. Such conductivity within the substrate may allow reliable back-gate control for the gain of a component bipolar device of the thyristor.
1. A thyristor-based semiconductor memory device, comprising:
a supporting substrate comprising at least one of semiconductor material and conductor material;
dielectric layered on the supporting substrate;
a layer of silicon disposed on the dielectric;
the layer of silicon comprising doped regions of opposite sequential polarity that define a thyristor;
a wordline electrode disposed in insulated relationship over a base region of the thyristor;
a MOSFET with source, body and drain regions formed in at least a further portion of the layer of silicon over the dielectric, the drain region of the MOSFET physically shared in common, contiguous relationship with a cathode-emitter region of the thyristor; and
a bias circuit electrically coupled to the supporting substrate to enable application of a given voltage to the supporting substrate when the memory device is operating;
wherein at least a portion of the supporting substrate is conductively and operatively configured to enable receipt and delivery of the given applied voltage to a location beneath the thyristor to impart a back-side bias electric field effect to the thyristor when the bias circuit applies the given voltage to the supporting substrate.
2. The memory device of claim 1 , in which the interface region of the supporting substrate beneath the thyristor and the MOSFET comprises a given dopant of density at least about 10 16 per cm 3 .
3. The memory device of claim 2 , wherein the bias circuit is further operably configured to, when the device is operating, adjust the magnitude of the voltage applied to the supporting substrate with a voltage-versus-temperature dependency sufficient to compensate at least in part a given sensitivity in gain of the thyristor with respect to temperature.
4. The memory device of claim 2 , in which the bias circuit is electrically coupled to an ohmic contact formed in the supporting substrate; and
the interface region of the supporting substrate of the given dopant density comprises a lateral extent that encompasses the ohmic contact.
5. The memory device of claim 1 , in which the bias circuit is operably configured to, when the device is operating, sense a temperature and adjust the magnitude of the voltage bias applied to at least one of the electrode and the supporting substrate based on the temperature sensed.