Method of manufacturing oxide isolated semiconductor device utilizing selective etching technique

Abstract

In the production of a semiconductor integrated circuit device including a selective oxidation step at a high temperature using a nitride film as a mask for isolating respective element regions in a semiconductor wafer with oxidized regions, electrode contact regions and active regions are successively formed in each element region to be surrounded by the oxidized regions and thin oxide films are formed on exposed surfaces of the electrode contact regions, the thin semiconductor oxide films are removed simultaneously by immersed etching, and then electrode metal layers are formed thereon. The thickness of the oxide layer on which the electrode metal layers are formed is maintained almost uniform to ensure the isolation effect. Since a buried region in each element region is required only to make partial contact with the contact region at the bottom portion, the integration density of the elements in the integrated circuit can be increased.

What is claimed is:  .[.1. A method of manufacturing a semiconductor device comprising the steps of: 
     
           A method of manufacturing a semiconductor integrated circuit device comprising the .Iadd.succeeding .Iaddend.steps of: (a) selectively forming a first heavily doped region of a first conductivity type in the surface portion of a semiconductor substrate of a second conductivity type;   (b) growing an epitaxial layer of said second conductivity type on the surface of said substrate and thereby burying said first heavily doped region;   (c) selectively etching away said epitaxial layer to form .Iadd.a .Iaddend.recessed .[.portions.]. .Iadd.portion .Iaddend.and selectively oxidizing said epitaxial layer in said recessed .[.portions.]. .Iadd.portion .Iaddend.to form .Iadd.an .Iaddend.oxidized .[.regions.]. .Iadd.region .Iaddend.extending to the .[.substrate.]. .Iadd.buried region.Iaddend., thereby forming respective element regions isolated from each other by said oxidized .[.regions and.]. .Iadd.region, .Iaddend.at least one element region having a main region and an .[.electrode contact.]. .Iadd.additional .Iaddend.region surrounded by said oxidized region .[.and electrically connected to said main region through said.]..Iadd., said main region and said additional region being formed on a common .Iaddend.buried .[.first heavily doped.]. region;   (d) .[.selectively diffusing impurities into said main region to form a second semiconductor region of said second conductivity type and a third semiconductor region of said first conductivity type and into said electrode contact region to convert the conductivity type and form an electrode contact region of said first conductivity type extending to said buried region and forming simultaneously oxide films on exposed surfaces,.]. .Iadd.diffusing an impurity into said main region to form a second semiconductor region of said second conductivity type and forming simultaneously an oxide film thereon;   (e) diffusing an impurity into said additional region to form an electrode contact region of said first conductivity type extending to said buried region and forming simultaneously an oxide film thereon;   (f) selectively diffusing an impurity into said second region to form a third semiconductor region of said first conductivity type and forming simultaneously an oxide film thereon, .Iaddend.said third semiconductor region and said electrode contact region being covered with oxide films of smaller thickness than .[.those.]. .Iadd.that .Iaddend.of .[.other portions.]. .Iadd.the oxide film on said second region; .Iaddend.   .[.(e).]. .Iadd.(g) .Iaddend.opening a window in said oxide film on said second semiconductor region;   .[.(f).]. .Iadd.(h) .Iaddend.uniformly etching away the oxide .[.film.]. .Iadd.films .Iaddend.to a predetermined depth so that .[.said thin oxide films on.]. .Iadd.the surfaces of .Iaddend.said third semiconductor region and said electrode contact region are exosed .[.:.]. .Iadd.; .Iaddend.and   .[.(g).]. .Iadd.(i) .Iaddend.forming metal electrodes on the exposed semiconductor .[.surface.]. .Iadd.surfaces .Iaddend.and on .[.the   
     
     
        remaining oxide film.]. .Iadd.said oxidized region.Iaddend.. .Iadd. 6.  A method of manufacturing a semiconductor integrated circuit device according to claim 5, wherein the impurities used for diffusing in said steps (d), (e), and (f) are boron, phosphorus, and arsenic, respectively. .Iaddend.