V-MOS Field effect transistor for a dynamic memory cell having improved capacitance
AssigneeBurroughs Corporation
InventorMark A. Vinson
Life of this patent
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Abstract
This disclosure relates to a V-MOS field effect transistor which is provided with enhanced source capacitance to provide a single transistor dynamic memory cell. The formation of the source area is achieved by masking the silicon substrate, opening an aperture in the mask and then etching the silicon substrate in such a manner as to undercut the mask so that the mask provides a shield to subsequent ion implanting of the source area. Both P and N type dopants can be separately implanted with different energy levels so as to form an enhanced PN junction capacitance for the device. Such a field effect transistor can be achieved without the formation of a graded dopant concentration in the channel between the source and drain areas of the transistor.
Claims8
A field effect transistor comprising:
- a monocrystalline unitary substrate of one conductivity type, said substrate having a surface and uniform dopant concentration;
- a region in said substrate adjacent to said surface and having a conductivity of a second conductivity type;
- a V-shaped recess in said substrate extending from said surface through said region of said second conductivity type, said recess being defined by recess surfaces;
- a second region of said second conductivity type in said unitary substrate, said second region being formed adjacent to said recess surface at least at the tip of the V by implanting ions through an aperture that overlies and is smaller than the top of said V:
- an oxide layer covering the surfaces of the V-shaped recess;
- and
- a gate electrode material covering at least a portion of said oxide layer in said V-shaped recess.
A field effect transistor comprising:
- a monocrystalline unitary substrate of one conductivity type, said substrate having a surface and uniform dopant concentration;
- a region in said substrate adjacent to said surface and having a conductivity of a second conductivity type;
- a V-shaped recess in said substrate extending from said surface through said region of said second conductivity type, said recess being defined by recess surfaces;
- a second region of said second conductivity type in said unitary substrate, said second region being formed adjacent to said recess surfaces at least at the tip of the V by implanting ions through an aperture that overlies and is smaller than the top of said V;
- a third region of said one conductivity type but with a greater concentration of ions, portions of said third region being formed adjacent to said second region by ion implantation through said aperture;
- an oxide layer covering the surfaces of said V-shaped recess;
- and
- a gate electrode layer covering at least a portion of said oxide layer in said V-shaped recess.
Dependencies are inferred from the claim text.