Nonvolatile semiconductor memory device capable of controlling mutual timing of write voltage pulse and transfer voltage pulse

• US 6,252,798 B1
• Filed: 06/25/1998
• Issued: 06/26/2001
• Est. Priority Date: 06/27/1997
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Satoh, Shinji, Tanzawa, Toru, Shirota, Riichiro
• Primary Examiner(s): Tran, Andrew Q.
• Application Number:
  US09/104,163
• Time in Patent Office: 1,097 Days
• Field of Search: 365/185.17, 365/185.02, 365/185.19, 365/185.23
• US Class Current: 365/185.02
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/08 Address circuits; Decoders; Word-line control circuits
• CPC Class Codes: G11C 16/32 Timing circuits

Abstract

A nonvolatile semiconductor memory device comprises a memory cell array having plural electrically erasable memory cells including a gate, a source, a drain, and an electric charge accumulation layer each disposed in a matrix form. A data writing section writes data into memory cells in this memory cell array. A data reading section reads out data in memory cells of the memory cell array. A data erasing section erases data in memory cells of the memory cell array. A control section controls, when applying a first signal to the gate in a specified memory inhibited of writing and applying a second signal to a node capacitively coupled to at least one of source and drain, in writing data into the memory cells, so that the second signal may fall later than the first signal.

Claims

1. A non-volatile semiconductor memory device comprising:

a memory cell array having cell strings each of which is constituted of a plurality of memory cells connected in series, each of said memory cells having at least a control gate; and

a control circuit that, at a time of programming, applies a write voltage pulse to the control gate of a memory cell selected from the plurality of memory cells constituting the cell strings, and that, at the time of programming, applies a transfer voltage pulse to non-selected memory cells,

wherein said control circuit changes a signal level of the transfer voltage pulse prior to the change in a signal level of the write voltage pulse and wherein said control circuit controls the timings of the write voltage pulse and the transfer voltage pulse in such a manner that the transfer voltage pulse falls when the write voltage pulse is at a high level.

2. The non-volatile semiconductor memory device according to claim 1, wherein the write voltage pulse is generated on the basis of a first signal, the transfer voltae pulse is generated on the basis of a second signal, and said non-volatile semiconductor memory device further comprises a delay circuit for delaying the first signal with respect to the second signal.

3. The non-volatile semiconductor memory device according to claim 2, wherein the delay circuit includes a delay element, an input terminal and an output terminal, the second signal is input into the input terminal, the first signal is output from the output terminal, and the first signal is delayed with respect to the second signal for a period of time which corresponds to a delay time of the delay element.

4. The non-volatile semiconductor memory device according to claim 2, further comprising a first circuit for outputting the first signal and a second circuit for outputting the second signal when a third signal is input into the first circuit and the second circuit.

5. The non-volatile semiconductor memory device according to claim 4, wherein the first circuit includes a delay element which delays the third signal, and the first signal is generated on the basis of a signal delayed for a period of time which corresponds to a delay time of the delay element.

6. The non-volatile semiconductor memory device according to claim 2, wherein the first and second signals are generated by a binary counter which receives an input clock and outputs a plurality of clocks and a logic circuit which outputs a result of logic calculation for the plurality of clocks.

7. The non-volatile semiconductor memory device according to claim 1, wherein the control circuit controls the timings of the write voltage pulse and the tansfer voltage pulse in such a manner that a beginning of a fall time of the write voltage pulse is set later than a beginning of a fall time of the transfer voltage pulse.

8. The non-volatile semiconductor memory device according to claim 1, wherein the control circuit controls the timings of the write voltage pulse and the transfer voltage pulse in such a manner that an end of a fall time of the write voltage pulse is set later than an end of a fall time of the transfer voltage pulse.

9. A non-volatile semiconductor memory device comprising:

a memory cell array having cell strings arranged in a matrix form, each of said cell strings constituted of a plurality of memory cells which include control gates, sources and drains and are connected in series in such a manner that adjacent ones of the memory cells share one source and one drain;

a plurality of bit lines connected to one end of each of the cell strings and arranged in a column direction of the memory cell array;

a source line connected to the other end of each of the cell strings; and

a control circuit that, at a time of programming, applies a write voltage pulse to the control gate of memory cell selected from the plurality of memory cells constituting the cell strings, and that, at the time of programming, applies a transfer voltage pulse to non-selected memory cells,

wherein said control circuit changes a signal level of the transfer voltage pulse prior to the change in a sismal level of the write voltage pulse and wherein said control circuit controls the timings of the write voltage pulse and the transfer voltage pulse in such a manner that the transfer voltage pulse falls when the write voltage pulse is at a high level.

10. The non-volatile semiconductor memory device according to claim 9, wherein said control circuit controls the timings of the write voltage pulse and the transfer voltage pulse in such a manner that an end of a fall time of the transfer voltage pulse is set earlier than an end of a fall time of the write voltage pulse.