Nonvolatile semiconductor memory device
First Claim
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1. A nonvolatile semiconductor memory device comprising:
- a semiconductor substrate with a main surface;
a plurality of memory cell units formed on said main surface of said semiconductor substrate, each of said memory cell units having a plurality of memory cells connected in one unit, each of said memory cells containinga first charge accumulation layer formed on said main surface of said semiconductor substrate in an insulating manner,a first control gate formed on said first charge accumulation layer in an insulating manner, andtwo first diffusion layers formed at said main surface of said semiconductor substrate on both side of said first charge accumulation layer, at least one of said two first diffusion layers being shared by adjacent one of said memory cells, thereby connecting said memory cells adjacent to each other;
a plurality of first select transistors connected to one end of each of said plurality of memory cell units via one of said first diffusion layers located at the one end,each of said plurality of first select transistors containing a second control gate and a source and a drain region and being connected in series by adjacent one of said first select transistors sharing one of said source and said drain region, said second control gate being connected to each of a plurality of select gate lines,at least one of said plurality of first select transistors further containinga second charge accumulation layer on said main surface of said semiconductor substrate and under said second control gate in an insulating manner; and
a data line connected to at least two adjacent ones of said memory cell units via said plurality of first select transistors.
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Abstract
A nonvolatile semiconductor memory device has reduced parasitic capacitance at a select transistor obtained by providing a depletion-mode select transistor with a charge accumulation layer, virtually making a gate insulating film thicker, or providing under the gate insulating film a channel layer that is of a same conductivity type as that of a source and drain regions and connects thereto, thereby enabling the potential of the select gate to be almost fixed at a desired value, preventing a faulty operation and making it possible to cause the select transistor to operate at high speed.
84 Citations
25 Claims
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1. A nonvolatile semiconductor memory device comprising:
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a semiconductor substrate with a main surface; a plurality of memory cell units formed on said main surface of said semiconductor substrate, each of said memory cell units having a plurality of memory cells connected in one unit, each of said memory cells containing a first charge accumulation layer formed on said main surface of said semiconductor substrate in an insulating manner, a first control gate formed on said first charge accumulation layer in an insulating manner, and two first diffusion layers formed at said main surface of said semiconductor substrate on both side of said first charge accumulation layer, at least one of said two first diffusion layers being shared by adjacent one of said memory cells, thereby connecting said memory cells adjacent to each other; a plurality of first select transistors connected to one end of each of said plurality of memory cell units via one of said first diffusion layers located at the one end, each of said plurality of first select transistors containing a second control gate and a source and a drain region and being connected in series by adjacent one of said first select transistors sharing one of said source and said drain region, said second control gate being connected to each of a plurality of select gate lines, at least one of said plurality of first select transistors further containing a second charge accumulation layer on said main surface of said semiconductor substrate and under said second control gate in an insulating manner; and a data line connected to at least two adjacent ones of said memory cell units via said plurality of first select transistors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A nonvolatile semiconductor memory device comprising:
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a semiconductor substrate with a main surface; a plurality of memory cell units formed on said main surface of said semiconductor substrate, each of said memory cell units having a plurality of memory cells connected in one unit, each of said memory cells containing a first charge accumulation layer formed on said main surface of said semiconductor substrate in an insulating manner, a first control gate formed on said charge accumulation layer in an insulating manner, and two first diffusion layers formed at said main surface of said semiconductor substrate on both side of said charge accumulation layer, at least one of said first diffusion layers being shared by adjacent one of said memory cells, thereby connecting said memory cells adjacent to each other; a plurality of first select transistors connected to one end of each of said plurality of memory cell units via one of said diffusion layers located at the one end, each of said plurality of first select transistors containing a gate insulating film formed on said main surface of said semiconductor substrate, a second control gate formed on said gate insulating film, and a source and a drain region formed at said main surface of said semiconductor substrate on both side of said second control gate, at least one of said source and said drain region being shared by adjacent one of said select transistors and connecting said adjacent one of said select transistors in series, said second control gate being connected to a corresponding one of a plurality of control gate lines, and said gate insulating film of at least one of said first select transistors being made thicker than said gate insulating film of another one of said first select transistors; and a data line connected to at least two adjacent ones of said memory cell units via said plurality of first select transistors. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A nonvolatile semiconductor memory device comprising:
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a semiconductor substrate with a main surface; a plurality of memory cell units formed on said main surface of said semiconductor substrate, each of said memory cell units having a plurality of memory cells connected in one unit, each of said memory cells containing a first charge accumulation layer formed on said main surface of said semiconductor substrate in an insulating manner, a first control gate formed on said charge accumulation layer in an insulating manner, and two first diffusion layers formed at said main surface of said semiconductor substrate on both side of said charge accumulation layer, at least one of said two first diffusion layers being shared by adjacent one of said memory cells, thereby connecting said memory cells adjacent to each other; a plurality of first select transistors connected to one end of each of said plurality of memory cell units via one of said diffusion layers located at the one end, each of said plurality of first select transistors containing a second control gate formed on said main surface of said semiconductor substrate in an insulating manner, and a source and a drain region formed at said main surface of said semiconductor substrate on both side of said second control gate, at least one of said source and said drain region being shared by adjacent one of said first select transistors and connecting said adjacent one of said memory cells in series, said second control gate being connected to a corresponding one of a plurality of control gate lines, and at least one of said plurality of first select transistors having a second diffusion layer of a same conductivity type as that of said source and said drain region in said semiconductor substrate, said second diffusion layer being electrically connected to said source and said drain region; and a data line connected to at least two adjacent ones of said memory cell units via said plurality of first select transistors. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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Specification