A semiconductor memory device comprises memory cells, a bitline connected to the memory cells, a read circuit including a precharge circuit, and a first transistor connected between the bitline and the read circuit, wherein a first voltage is applied to a gate of the first transistor when the precharge circuit precharges the bitline, and a second voltage which is different from the first voltage is applied to the gate of the first transistor when the read circuit senses a change in a voltage of the bitline.

Semiconductor memory device.

A floating gate type semiconductor non-volatile memory injects carriers from a carrier supply region to a floating gate by a phenomenon called "punch-through" injection in which a space charge region is formed in a semiconductor substrate between the carrier supply region and a carrier injection region so as to accelerate the carriers and inject them into the floating gate without forwardly biasing the carrier injection region or the substrate.

Semiconductor nonvolatile memory

A semiconductor integrated circuit has a central processing unit and a rewritable nonvolatile memory area disposed in an address space of the central processing unit. The nonvolatile memory area has a first nonvolatile memory area and a second nonvolatile memory area, which memorize information depending on the difference of threshold voltages. The first nonvolatile memory area has the maximum variation width of a threshold voltage for memorizing information set larger than that of the second nonvolatile memory area. When the maximum variation width of the threshold voltage for memorizing information is larger, since stress to a memory cell owing to a rewrite operation of memory information becomes larger, it is inferior in a point of guaranteeing the number of times of rewrite operation; however, since a read current becomes larger, a read speed of memory information can be expedited. The first nonvolatile memory area can be prioritized to expedite a read speed of the memory information and the second nonvolatile memory area can be prioritized in guaranteeing the number of times of rewrite operation of memory information more.

Semiconductor Integrated circuit

A method for fabricating a semiconductor device includes forming a recess gate over a semiconductor substrate. A gate spacer is formed on a sidewall of the recess gate. The semiconductor substrate in a landing plug contact region is soft-etched to form a recess having a rounded profile. A sidewall spacer is formed over the gate spacer and a sidewall of the recess. An insulating film is formed over the semiconductor substrate. The insulating film is selectively etched to form a landing plug contact hole. A conductive layer in the landing plug contact hole is filled to form a landing plug.

Semiconductor Device and Method for Fabricating the Same

An asymmetrical N-channel IGFET and an asymmetrical P-channel IGFET are disclosed. One or both IGFETs include a lightly doped drain region, heavily doped source and drain regions, and an ultra-heavily doped source region. Preferably, the heavily doped source region and lightly doped drain region provide channel junctions. Forming a first asymmetrical IGFET includes forming a gate with first and second opposing sidewalls over a first active region, applying a first ion implantation to implant lightly doped source and drain regions into the first active region, applying a second ion implantation to convert substantially all of the lightly doped source region into a heavily doped source region without doping the lightly doped drain region, forming first and second spacers adjacent to the first and second sidewalls, respectively, and applying a third ion implantation to convert a portion of the heavily doped source region outside the first spacer into an ultra-heavily doped source region without doping a portion of the heavily doped source region beneath the first spacer, and to convert a portion of the lightly doped drain region outside the second spacer into a heavily doped drain region without doping a portion of the lightly doped drain region beneath the second spacer. A second asymmetrical IGFET is formed in a related manner. Advantageously, one or both IGFETs have low source-drain series resistance and reduce hot carrier effects.

Asymmetrical N-channel and P-channel devices

PURPOSE:To improve integration degree by forming an N-well to build an N-channel transistor, thereafter by wet-etching the part by forming a thick oxide film and by providing a step to a surface of a P-type silicon substrate. CONSTITUTION:A P-type silicon substrate 1 is selectively oxidized to form a thick oxide film 22. The oxide film 22 is wet-etched to lower a substrate surface 23 on an N-well 2 relatively to the surface of the P-type silicon substrate 1. Then a first MOSFET 15 is formed to a region which is formed by wet- etching the P-type silicon substrate 1. A second MOSFET 16 is formed on the P-type silicon substrate 1 adjoining the N-well 2. According to this constitution, it is possible to restrain lap-up phenomenon, to cut down a distance between MOSFETs 15, 16 and to improve integration degree.

Tsukamoto Kazuhiro

Papers

Semiconductor integrated circuit device