Hitachi, Ltd.

Makoto Motoyoshi

Satoshi Meguro

Osamu Minato

Norio Suzuki

Takashi Hashimoto

Toshiaki Yamanaka

Yoshio Sakai

Naotaka Hashimoto

Toru Kaga

Atsuyoshi Koike

Kiyofumi Uchibori

Shigeru Honjou

Shuji Ikeda

Kouichi Nagasawa

Kiyoshi Nagai

The manufacture of a memory cell of the type employing a pair of cross-coupled CMOS inverters of a SRAM is disclosed in which the load MISFETs are stacked above the semiconductor substrate and over the drive MISFETs. The manufacture of each load MISFET consists of forming source, drain and channel regions within the same polycrystalline silicon film, and a gate electrode consisting of a different layer conductive film, such as a polycrystalline film, than that of the drive MISFETs. The manufacture of the memory cell having such a stacked arrangement, facilitates the patterning of the source (drain) region and gate electrode of each load MISFET thereof to have an overlapping relationship with each other so as to increase the effective capacitance associated with each of the memory cell storage nodes. The gate electrodes of both the drive and load MISFETs are formed of n-type or of n-type and p-type polycrystalline silicon films, respectively, and electrical connections are formed between the drain regions of the first and second p-channel load MISFETs with that of the drain regions of the first and second n-channel drive MISFETs through separate polycrystalline silicon films, respectively. Also, there are formed electrical connections between the polycrystalline silicon gate electrodes of the first and second load MISFETs with that of drain regions of the second and first drive MISFETs, through the poly-Si gate electrodes of the first and second drive MISFETs, in each memory cell of the SRAM, respectively, furthermore.

Semiconductor integrated circuit device

A memory cell of the type a pair of cross-coupled CMOS inverters of a SRAM is disclosed in which the load MISFETs are stacked above the semiconductor substrate and over the drive MISFETS. Each load MISFET of a memory cell consists of a source, drain and channel region formed within the same polycrystalline silicon film, and a gate electrode consisting of a different layer conductive film than that of the drive MISFETs. In a memory cell having such a stacked arrangement, the source (drain) region and gate electrode of each load MISFET thereof are patterned to have an overlapping relationship with each other so as to increase the effective capacitance associated with each of the memory cell storage nodes. The gate electrodes of both the drive and load MISFETs are formed of n-type and p-type polycrystalline silicon films, respectively, and the drain regions of the first and second p-channel load MISFETs are electrically connected to the drain regions of the first and second n-channel drive MISFETs through separate polycrystalline silicon films, respectively. The polycrystalline silicon gate electrodes of the first and second load MISFETs are respectively electrically connected to the drain regions of the second and first drive MISFETs in each memory cell of the SRAM, furthermore.

A memory cell of the type employing a pair of cross-coupled CMOS inverters of a SRAM is disclosed in which the load MISFETs are stacked above the semiconductor substrate and over the drive MISFETs. Each load MISFET of a memory cell consists of a source, drain and channel region formed of a semiconductor strip, such as a polycrystalline silicon film strip, and a gate electrode consisting of a different layer conductive film than that of the drive MISFETs. In a memory cell having such a stacked arrangement, the source region and gate electrode of each load MISFET thereof are patterned to have a widely overlapping relationship with each other to form a capacitor element thereacross such that an increase in the overall capacitance associated with each of the memory cell storage nodes is effected thereby decreasing occurrence of soft error. The overlapping relationship for effecting the large capacitor element across the source and gate of the respective load MISFETs is provided by an ion implanting scheme of a p-type impurity into the semiconductor strip. A separate mask for ion-implantation for the formation of the source region of the load MISFET is added followed by the addition of the gate electrode thereof in a manner so as to have a widely overlapping relationship with that of the source region.

A memory cell of the type employing a pair of cross-coupled CMOS inverters of a SRAM is provided in which the load MISFETs are stacked above the semiconductor substrate and over the drive MISFETs. Each load MISFET of a memory cell consists of a source, drain and channel region formed of a semiconductor strip, such as a polycrystalline silicon film strip, and a gate electrode consisting of a different layer conductive film than that of the drive MISFETs. A wiring line, formed as a separate conductive layer, is provided in the stacking arrangement of the drive and load MISFETs of a memory cell for applying a ground potential to source regions of the drive MISFETs thereof.

In a memory cell of SRAM of CMOS type, load MISFET having a polycrystalline silicon film as area of source, drain and channel is stacked on drive MISFET, and gate electrodes of the drive MISFET and the load MISFET are constituted by conductive films in different layers. Area of source and drain provided on the polycrystalline silicon film has an overlapped area with the gate electrode of the load MISFET.

Herein disclosed is a semiconductor integrated circuit device having a SRAM, in which two MISFETs of a flip-flop circuit of a memory cell are connected directly with an n.sup.+ -type drain region so that they are cross coupled; and in which a p.sup.+ -type semiconductor region is formed below a direct contact part by making use of the mask used in the step of forming contact holes for the direct contact part. The p.sup.+ -type semiconductor region aids as a barrier to prevent soft errors of the SRAM due to .alpha.-particles.

Semiconductor integrated circuit device and process for fabricating the

After contact holes for the P- and N-type source or drain regions of P- and N-channel MOSFETs have been made at a common step, an N-type impurity is ion-implanted into at least the N-type source or drain regions through the contact holes. The N-type impurity is annealed to fornm an N-type region which is deeper than the N-type source or drain regions. During the annealing treatment, the N-type source or drain regions are covered with an insulating film.

Process for fabricating semiconductor integrated circuit devices

After contact holes for the P- and N-type source or drain regions of P- and N-channel MOSFETs have been made at a common step, an N-type impurity is ion-implanted into at least the N-type source or drain regions through the contact holes. The N-type impurity is annealed to form an N-type region which is deeper than the N-type source or drain regions. During the annealing treatment, the N-type source or drain regions are covered with an insulating film.

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Hachioji, Japan

Makoto Motoyoshi