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Semiconductor device with no stress generated at the trench corner portion and the method for making the same

  • US 4,894,695 A
  • Filed: 03/17/1988
  • Issued: 01/16/1990
  • Est. Priority Date: 03/23/1987
  • Status: Expired due to Term
First Claim
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1. A semiconductor device comprising:

  • a semiconductor substrate having a main surface, a prescribed impurity concentration of a first conductivity type and a trench;

    a thick insulating film formed on either a bottom portion or a sidewall portion of said trench, an end portion of said thick insulating film extending in either a vertical upward direction when said thick insulating film is formed on the bottom portion or a horizontal direction when the thick insulating film is formed on the sidewall portion;

    a thin insulating film extending in the direction orthogonal to said thick insulating film and connected to the end portion of said thick insulating film; and

    a first impurity region of a second conductivity type formed in said semiconductor substrate on either the sidewall portion or the bottom portion and the sidewall portion of said trench on which said thick insulating film is not formed, only in the side portion or lower portion of said thin insulating film, said thick insulating film is formed byforming a two-layer film constituted by an oxide film and a nitride film on the main surface of said semiconductor substrate, side portions and a portion of the bottom portion of the trench, andforming a selective oxide film to form said thick insulating film on the bottom portion of the trench of said semiconductor substrate by oxidizing said semiconductor substrate with said two-layer film formed thereon, wherebythe direction of extension of the end portion of said selective oxide film changing from horizontal to vertical upward with a large curvature.

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