Sharp Kabushiki Kaisha Corporation

Masanori Yoshimi

Shinichi Sato

Yoshimitsu Yamauchi

Keizo Sakiyama

Takuji Tanigami

Naoyuki Shinmura

Satoru Yamagata

Takayuki Taniguchi

Kenji Hakozaki

Kiyoshige Omori

In a method for manufacturing a memory cell of a nonvolatile semiconductor memory, a floating gate, first insulating film and control gate are successively stacked on a tunnel oxide film formed on a substrate of the nonvolatile semiconductor memory. The control gate, the first insulating film and the floating gate are patterned in stripes. Subsequently, a damaged portion of the tunnel oxide film immediately below a sidewall of the floating gate is removed by isotropic etching. A second insulating film is deposited to cover the control gate, sidewalls of the first insulating film, the floating gate and the tunnel oxide film. Thereby, a variation in threshold voltages between memory cells is suppressed.

Method for manufacturing nonvolatile semiconductor memory with narrow variation in threshold voltages of memory cells

The present invention provides a process for fabricating semiconductor device comprising the steps of: forming an etching-stop layer on a semiconductor substrate; patterning the etching-stop layer so that the etching-stop layer remains in a region to be an active region and is removed from a region to be a device isolation region, followed by forming a trench in the region to be the device isolation region; depositing on the semiconductor substrate an insulating film having a thickness greater than or equal to the depth of the trench; forming a resist pattern having an opening above the etching-stop layer above the active region adjacent to a device isolation region whose width is greater than or equal to a predetermined value, followed by etching the insulating film using the resist pattern as a mask; and polishing the insulating film existing on the resulting semiconductor substrate for flattening after removing the resist pattern.

Process for fabricating a semiconductor device

A plurality of blocks of memory cell transistors are formed on the respective isolated wells. In a write stage, a predetermined write-stage well voltage is applied to the well of a selected block including the memory cell transistors to be subjected to a write operation, a bias voltage is applied to the well of each of the remaining, non-selected blocks to increase a threshold voltage of the memory cell transistors of each non-selected block, in comparison with a threshold voltage determined by the predetermined write-stage well voltage, and a voltage is applied to the control gates of the memory cell transistors of each non-selected block to reduce a difference between a potential of the floating gate of each memory cell transistor of each non-selected block and a write-stage drain voltage applied to the drain of the memory cell transistor through the associated bit line such that a source-drain leak current of each memory cell transistor in the non-selected blocks falls in a permissible range.

Nonvolatile semiconductor storage device having a plurality of blocks of

In the nonvolatile semiconductor memory including a memory cell array having memory cells arranged in a matrix of the present invention, the memory cell array includes: a semiconductor substrate; a tunnel oxide film formed on the semiconductor substrate; floating gates formed on the tunnel oxide film; first insulating films formed on the floating gates; and control gates formed on the first insulating films, wherein each of the floating gates includes a first polysilicon film and second polysilicon films, the second polysilicon films being formed on both sides of the first polysilicon film, second insulating films are formed on the tunnel oxide film between the first polysilicon films, the second insulating films having a predetermined thickness which is thinner than that of the first polysilicon films, and the second polysilicon films are formed on the second insulating films.

Nonvolatile semiconductor memory with a floating gate that has a bottom

This invention is directed to a process for the fabrication of a stacked semiconductor nonvolatile memory device, which process is adapted to define a longitudinal length of a floating gate in self-alignment with overlying control gate and interlayer insulating film by etching, without severely damaging the underlying semiconductor substrate.

Growing community of inventors

Fukuyama, Japan

Masanori Yoshimi