Abstract:
A semiconductor memory device includes a memory cell array, data buffer, and column switch. The data buffer senses the potential of a bit line to determine data in a selected memory cell and hold readout data in a read. The data buffer detects both whether the whole data buffer holds “0” data and whether the whole data buffer holds “1” data. The column switch selects part of the data buffer and connects the part to a bus.
Abstract:
A semiconductor memory device includes a memory cell array, data buffer, and column switch. The data buffer senses the potential of a bit line to determine data in a selected memory cell and hold readout data in a read. The data buffer detects both whether the whole data buffer holds “0” data and whether the whole data buffer holds “1” data. The column switch selects part of the data buffer and connects the part to a bus.
Abstract:
A semiconductor memory device includes a memory cell array, data buffer, and column switch. The data buffer senses the potential of a bit line to determine data in a selected memory cell and hold readout data in a read. The data buffer detects both whether the whole data buffer holds “0” data and whether the whole data buffer holds “1” data. The column switch selects part of the data buffer and connects the part to a bus.
Abstract:
In a virtual ground semiconductor memory device such as an EPROM or a Flash EPROM, a program disturb inhibited unit is operatively connected to a memory array. The memory array includes a plurality of metal virtual ground and bit lines, with at least two bit line selection transistors connected to each of the metal lines. The program disturb inhibited is connected to each virtual ground line and each bit line. In this structure, one metal pitch is connected to two buried diffusion lines. The program inhibited unit includes a plurality of program disturb inhibited transistors, wherein each transistor is connected between a virtual ground and a bit line. A DWL and a DWR dummy line are connected to control the plurality of program disturb inhibited transistors. By combining the program disturb inhibit unit with the memory array, a conventional array structure which has only been suitable for MROM applications can be applied to an EPROM or a Flash EEPROM, allowing the cell size to be reduced.
Abstract:
An asymmetric multilevel memory cell provides an inhibited source read current. The inhibited source read current dramatically reduces the likelihood of a cell type misread error for a memory array comprising multilevel cells. The method for fabricating the asymmetric multilevel memory cell comprises a source only implant, formation of a spacer on the drain side of the gate prior to source/drain implant, and the resultant formation of an offset region disposed between the channel and the drain. The offset region is not controlled by the gate voltage. The drain current at 1.5 volts is more than 3.5 times larger than the source current at 1.5 volts for spacer width of 0.12 micrometers. Asymmetric multilevel memory cells in a memory array, where the cells have a common source configuration, are accurately read in one direction because neighboring cells on the word line have substantially lower source current than the read cell drain current.
Abstract:
A method for programming a semiconductor memory device, such as an EPROM or a Flash EPROM, which combines the advantages of ramping down a source voltage with the advantages associated with increasing a gate voltage. A programming period is divided into a program disturbance inhibited period and a program period. The programming period is further divided into sub-program periods, with each sub-program period having a program disturbance and a program period. A wordline WL voltage may increase with each sub-program period to improve the programming speed. Also, the program disturbance period may only be performed for the first sub-program period. Each sub-program period may also include a verify period, in order to implement a program and verify technique suitable for programming multi-level Flash EPROMS.
Abstract:
A method and device for programming multiple levels of voltage states in a memory cell. A program and verify memory cell device includes a memory cell coupled with at least one dummy cell, the devices sharing common drain, gate, and source nodes. The threshold voltage of each dummy cell is set to a target threshold level for programming the memory cell. A stair-step sequence of pulses is used to program and verify the memory cell. A constant current source can also be coupled between the source node and the ground. The programming steps for this device include applying a high voltage to the drain and gate nodes, and coupling the source to level while starting the program pulse, then establishing a constant current at the source to pull it from high to level, and then applying program and verify pulses at the memory cell gate. A self convergence memory cell device includes the parallel connected memory and dummy cells above, but with at least one current sensing device coupled between the dummy cell and the drain. The programming steps for this device include applying a high voltage to the drain and gate nodes, and coupling the source to level while starting the program pulse, then establishing a constant current at the source to pull it from high to level, and then using the current sensing device to pull down the drain when a certain dummy cell current is reached upon subsequent application of programming pulses.