Method of making a diamond shaped gate mesh for cellular MOS transistor array
AssigneeMicrel, Inc.
InventorsJames C. Moyer, Martin J. Alter, Helmuth R. Litfin
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Abstract
A cellular transistor structure is disclosed which incorporates a polysilicon gate mesh. In one embodiment, the silicon under the polysilicon is of an N-type while the exposed area not covered by the polysilicon is doped with a P dopant to form P-type source and drain regions. Metal strips are used to contact the rows of source and drain cells. By forming the openings in the polysilicon mesh to be in a diamond shape (i.e., having a long diagonal and a short diagonal), the source and drain metal strips, arranged in the direction of the short diagonals, can be made wider and shorter, thus reducing the on-resistance of the transistor without increasing the area of the transistor.
Claims10
A method of forming an MOS transistor comprising the steps of:
- forming a conductive gate overlying and insulated from a top surface of a semiconductor material of a first conductivity type, said conductive gate being a mesh having a plurality of substantially identical openings, each of said openings approximating an elongated diamond shape having a long diagonal and a short diagonal,
- doping said gate and said openings with a dopant of a second conductivity type, using said gate as a mask to form source regions and drain regions of said MOS transistor self-aligned with said gate,
- said source regions and said drain regions being located in alternate rows of said openings, where each row is along the direction of said short diagonal of said openings,
- regions of said semiconductor material underlying said gate being of said first conductivity type to form channel regions of said MOS transistor;
- forming a first conductive strip of material overlying and electrically contacting central portions of a first row of said source regions, said first conductive strip for being connected to a source voltage;
- and
- forming a second conductive strip of material overlying and electrically contacting central portions of a second row of said drain regions adjacent to said first row of said source regions.
Dependencies are inferred from the claim text.