A content addressable memory cell includes a first floating body transistor and a second floating body transistor. The first floating body transistor and the second floating body transistor are electrically connected in series through a common node. The first floating body transistor and the second floating body transistor store complementary data.

Methods of maintaining a state of a memory cell without interrupting access to the memory cell are provided, including applying a back bias to the cell to offset charge leakage out of a floating body of the cell, wherein a charge level of the floating body indicates a state of the memory cell; and accessing the cell.

An object is to shorten the time for rewriting data in memory cells. A memory module includes a first memory cell, a second memory cell, a selection transistor, and a wiring WBL1. The first memory cell includes a first memory node. The second memory cell includes a second memory node. One end of the first memory cell is electrically connected to the wiring WBL1 through the selection transistor. The other end of the first memory cell is electrically connected to one end of the second memory cell. The other end of the second memory cell is electrically connected to the wiring WBL1. When the selection transistor is on, data in the first memory node is rewritten by a signal supplied through the selection transistor to the wiring WBL1. When the selection transistor is off, data in the first memory node is rewritten by a signal supplied through the second memory node to the wiring WBL1.

An object is to shorten the time for rewriting data in memory cells. A memory module includes a first memory cell, a second memory cell, a selection transistor, and a wiring WBL1. The first memory cell includes a first memory node. The second memory cell includes a second memory node. One end of the first memory cell is electrically connected to the wiring WBL1 through the selection transistor. The other end of the first memory cell is electrically connected to one end of the second memory cell. The other end of the second memory cell is electrically connected to the wiring WBL1. When the selection transistor is on, data in the first memory node is rewritten by a signal supplied through the selection transistor to the wiring WBL1. When the selection transistor is off, data in the first memory node is rewritten by a signal supplied through the second memory node to the wiring WBL1.

A semiconductor device, the device including: a first silicon layer including first single crystal silicon; an isolation layer disposed over the first silicon layer; a first metal layer disposed over the isolation layer; a second metal layer disposed over the first metal layer; a first level including a plurality of transistors, the first level disposed over the second metal layer, where the isolation layer includes an oxide to oxide bond surface, where the plurality of transistors include a second single crystal silicon region; and a third metal layer disposed over the first level, where a typical first thickness of the third metal layer is at least 50% greater than a typical second thickness of the second metal layer.

A stacked memory device includes a plurality of lower word lines extending in a first direction, a bit line positioned over the plurality of the lower word lines and extending in a second direction intersecting with the first direction, and a plurality of upper word lines positioned over the bit line and extending in the first direction. The stacked memory device also includes a plurality of lower memory cells including a lower capacitor and a lower switching element between the lower word lines and the bit line. The stacked memory device further includes a plurality of upper memory cells including an upper capacitor and an upper switching element between the bit line and the upper word lines.

A first dynamic flash memory cell formed on a first Si pillar 25a including an N.sup.+ layer 21a, a P layer 22a, and an N.sup.+ layer 21b, and a second dynamic flash memory cell formed on a second Si pillar 25b including a P layer 22b and an N.sup.+ layer 21c, the first dynamic flash memory cell and the second dynamic flash memory cell sharing the N.sup.+ layer 21b that is connected to a first bit line BL1, are stacked on top of one another on a P-layer substrate 20 to form a dynamic flash memory. In plan view, a first plate line PL1, a first word line WL1, a second word line WL2, and a second plate line PL2 extend in the same direction and are formed to be perpendicular to a direction in which the first bit line BL1 extends.

A first dynamic flash memory cell formed on a first Si pillar 25a including an N.sup.+ layer 21a, a P layer 22a, and an N.sup.+ layer 21b, and a second dynamic flash memory cell formed on a second Si pillar 25b including a P layer 22b and an N.sup.+ layer 21c, the first dynamic flash memory cell and the second dynamic flash memory cell sharing the N.sup.+ layer 21b that is connected to a first bit line BL1, are stacked on top of one another on a P-layer substrate 20 to form a dynamic flash memory. In plan view, a first plate line PL1, a first word line WL1, a second word line WL2, and a second plate line PL2 extend in the same direction and are formed to be perpendicular to a direction in which the first bit line BL1 extends.

Disclosed is a semiconductor device having a memory cell which comprises a transistor having a control gate and a storage gate. The storage gate comprises an oxide semiconductor and is able to be a conductor and an insulator depending on the potential of the storage gate and the potential of the control gate. Data is written by setting the potential of the control gate to allow the storage gate to be a conductor, supplying a potential of data to be stored to the storage gate, and setting the potential of the control gate to allow the storage gate to be an insulator. Data is read by supplying a potential for reading to a read signal line connected to one of a source and a drain of the transistor and detecting the change in potential of a bit line connected to the other of the source and the drain.

Disclosed is a semiconductor device having a memory cell which comprises a transistor having a control gate and a storage gate. The storage gate comprises an oxide semiconductor and is able to be a conductor and an insulator depending on the potential of the storage gate and the potential of the control gate. Data is written by setting the potential of the control gate to allow the storage gate to be a conductor, supplying a potential of data to be stored to the storage gate, and setting the potential of the control gate to allow the storage gate to be an insulator. Data is read by supplying a potential for reading to a read signal line connected to one of a source and a drain of the transistor and detecting the change in potential of a bit line connected to the other of the source and the drain.