Sankyo Company, Limited

Nec Corporation

Noriyuki Ohta

Tomoyuki Kurumada

Keisuke Murayama

Susumu Higashida

Katsuaki Matsui

Takao Yoshioka

Syoji Morimura

Eiko Mori

Toshimasa Toda

Hideo Horiuchi

Hisayou Osawa

Hisayou Ohsawa

Toshikatsu Jinbo

Noriaki Kodama

Hisayu Ohsawa

A nonvolatile semiconductor memory includes a cell array prepared by arranging erasable and programmable memory cell transistors in rows and columns, word lines arranged in correspondence with the respective rows of the cell array and connected to the control gates of the memory cell transistors, digit lines arranged in correspondence with the respective columns of the cell array and connected to the drains of the memory cell transistors, source lines connected to the sources of the memory cell transistors, and a source power supply circuit for applying a source voltage to the source lines in an erase operation. This memory erases by the source voltage data in the memory cell transistors in the rows and columns of the cell array. The source power supply circuit is a circuit including a first P-channel transistor which sets a current to be supplied to the source lines to a predetermined value in the erase operation in a range wherein the source voltage is lower than a predetermined potential, and a second P-channel transistor which sets the current to be supplied to the source lines so as to decrease faster than the current decreased by the characteristic of the first transistor with an increase in source voltage in a range wherein the source voltage is higher than the predetermined potential.

Nonvolatile semiconductor memory

A non-volatile semiconductor memory is composed of split gate type memory cell transistors, each of which comprises a source region and a drain region formed at a principal surface of a semiconductor substrate, separately from each other to form a channel region between the source region and the drain region. This channel region is divided into a first channel region adjacent to the drain region and a second channel region adjacent to the source region. A first gate insulator film is formed on a surface of the first channel region, and a control gate electrode is formed on the first gate insulator film. An insulator layer is formed on the source region and the drain region, and a second gate insulator film is formed on an upper surface and a pair of opposite side surfaces of the control gate electrode and on a surface of the second channel region. A floating gate electrode is formed on the second gate insulator film to have opposite ends terminating on the insulator layer formed on the source region and the insulator layer formed on the drain region, respectively.

Structure of split gate transistor for use in a non-volatile

A nonvolatile semiconductor memory device with improved writing characteristics. The memory device has memory cell transistors arranged in rows and columns. The memory cell transistors belonging to the same column share a source region and a drain region, and a channel region is disposed between the source and drain regions. The interval between the source and drain regions is the isolation width. Each of the memory cell transistors has a floating gate electrode disposed on the channel region with a first gate insulating film and a control gate electrode disposed on the floating gate electrode with a second gate insulating film. The floating gate electrode does not have a constant width and has a portion narrower than the isolation width which is free from the floating gate electrode. The narrower portion is typically formed as a constricted portion of the floating gate electrode.

Nonvolatile semiconductor memory device with shaped floating gate

Piperidine derivatives having the formula ##STR1## wherein R' represents an alkyl, an acyl, an alkoxycarbonyl, an amino or nitroso group;

Piperidine derivatives

A novel piperidine derivative having a stabilizing effect on a synthetic polymeric material and a composition comprising said piperidine derivative and a synthetic polymeric material.

A synthetic polymer composition stabilized against photo- and thermal-deterioration comprising a stabilizing amount of a compound having the formula ##STR1## wherein R' represents an alkyl, an acyl, an alkoxycarbonyl, an amino or nitroso group;

Polymer compositions containing piperidine derivatives as stabilizers

Novel piperidine derivatives of formula: ##STR1## (wherein 2 or 3 of R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 represent alkyl groups having from 1 to 4 carbon atoms and the remainder of R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are hydrogen atoms, and R.sub.6 represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a substituted alkyl group, an aliphatic acyl group, an alkoxycarbonyl group or an aralkoxycarbonyl group) are useful as stabilizers for synthetic polymers.

Novel piperidine derivatives for the stabilization of synthetic polymers

Piperidine-spiro-hydantoin derivatives having the formula ##SPC1## Wherein X represents oxygen atom or sulfur atom; n is an integer of 1 to 4 inclusive, and R represents various aliphatic or aromatic groups depending on the value of n. These compounds (I) are useful as stabilizers against photo and thermal deterioration of various synthetic polymers and can be prepared, for example, by reacting the corresponding 3-unsubstituted piperidine-spiro-hydantoin compound with the halide R-(X.sub.1).sub.n in which R and n are as defined herein and X.sub.1 is a halogen atom.

Piperidine-spiro-hydantoin derivatives and their use as stabilizers

4-Piperidone derivatives having the formulae ##SPC1## Wherein R represents a phenyl or naphthyl group which may be substituted with nitro, lower alkyl, halogen, hydroxyl, lower alkyl hydroxy, hydroxy lower alkyl or formyl or a 5- or 6-membered heterocyclic group having as a hetero atom at least one of oxygen atom, sulfur atom and nitrogen atom and R.sub.1 represents hydrogen atom or an alkyl group of 1 to 4 carbon atoms. They are useful as stabilizers for various synthetic polymers against their photo- and thermal-deteriorations and the 4-piperidone derivatives (II) are prepared from the corresponding 2,2,6,6-tetramethyl-4-oxopiperidine derivatives by reaction with an aldehyde and the 4-piperidone derivatives (I) are prepared from the 4-piperidone derivatives (II) through dehydration.

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Noriyuki Ohta