Dynamic random access memory device having a plurality of one-transistor type memory cells

Claim 1

A dynamic memory device comprising a semiconductor substrate of one conductivity type, a first pillar-like semiconductor portion of said one conductivity type connected to said substrate and extending upwardly from the surface of said substrate, a first impurity region of the opposite conductivity type formed at an upper end surface of said first pillar-like semiconductor portion, said first impurity region extending to an upper-most side surface of said first pillar-like semiconductor portion, a second impurity region of said opposite conductivity type formed at a lower side surface of said first pillar-like semiconductor portion with a region of said one conductivity type of said first pillar-like semiconductor portion being exposed at the upper side surface of said first pillar-like semiconductor portion between said first and second impurity regions, a first thin insulator film covering the exposed region of said one conductivity type at the upper side surface of said first pillar-like semiconductor portion, a second thick insulator film adjacent to said first thin insulator film and covering an upper part of said second impurity region, a third thin insulator film adjacent to said second thick insulator film and covering a lower part of said second impurity region, a second pillar-like semiconductor portion of said one conductivity type connected to said substrate and extending upwardly from the surface of said substrate to a height lower than said first pillar-like semiconductor portion, said second pillar-like semiconductor portion being located adjacently to said first pillar-like semiconductor portion via said third thin insulator film, the upper surface of said second pillar-like semiconductor portion being covered by said second thick insulator film, a bit line conductor connected to said first impurity region, and a word line conductor formed above said second pillar-like semiconductor portion and in contact with both of said first thin insulator film and said second thick insulator film, whereby a memory cell transistor is constituted by said first and second impurity regions, said region of one conductivity type between said first and second impurity regions, said first thin insulator film and said word line conductor and a memory cell capacitor is formed by said second impurity region, said third thin insulator film, said second pillar-like semiconductor portion and said first pillar-like semiconductor portion which is electrically connected to said second pillar-like semiconductor portion via said substrate.