Patent number 8541277 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to a non-volatile memory device, a method for fabricating the same, and a method for fabricating a semiconductor device by using the same; and more particularly, to a non-volatile memory device having a split gate type cell structure, a method for fabricating the same and a method for fabricating a semiconductor device by using the same.
"Generally, although an electric power is blocked, data stored in a memory cell of a non-volatile memory device is not damaged and thus, the non-volatile memory device has been widely used for a personal computer (PC) bias and for data storing of a set-top box, a printer and a network server. Recently, the non-volatile memory device has been used for a digital camera, a cellular phone and a smart card widely spread for public use.
"A flash memory device and an electrical erasable programmable read only memory (EEPROM) device are widely used as a representative non-volatile memory device. A cell program operation of the EEPROM device is performed by using a hot electron injection method and an erasion operation is performed by using a fouler nordheim (F-N) tunneling method.
"As for the hot electron injection method, a voltage is transferred to a cell drain and thus, a hot electron is formed in the drain side. Afterwards, a high voltage is transferred to a control gate, thereby injecting the hot electron formed in the drain side to a floating gate. Thus, a threshold voltage of the cell is increased. As for the F-N tunneling method, a high voltage is transferred to a source or a substrate and then, an electron injected to a floating gate by a program operation is discharged, thereby decreasing a threshold voltage of a cell.
"A cell of the EEPROM device is divided as an electrically tunneling oxide (ETOX) cell of a simply stacked structure and a split gate type cell comprised of two transistors per a cell.
"The ETOX cell is formed in a stacked structure of a floating gate for storing electric charges forming a gate and a control gate to which an operation power is transferred. Meanwhile, the split gate type cell uses a selection transistor and a cell transistor as one selection gate and is formed in a structure in which a predetermined portion of the selection gate is overlapped with a floating gate, and the remaining portion of the selection gate is placed on a substrate surface horizontally.
"A cell size of the ETOX cell is very small compared with that of the split gate type cell and thus, the ETOX cell is more advantageous to a high integration. Since the ETOX cell uses the hot electron injection method during a program operation, there is an advantage a program current is very large. However, during the program operation and a read operation, interference between the cells is happened, and during an erasion operation, an excessive erasion is happened. Thus, there is a disadvantage in that an operation reliability of the device is degraded.
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