Semiconductor device having a shallow trench isolation structure and a method for fabricating the same

A method for fabricating a semiconductor device having a shallow trench isolation structure including the steps of:

• forming mask patterns on a semiconductor substrate, exposing a portion of said semiconductor substrate;
• selectively etching an exposed region of said semiconductor substrate to a predetermined depth so as to form a first recess;
• forming ion-implantation buffer layers on the sidewalls of said first recess, exposing a bottom of said first recess;
• etching said semiconductor substrate using said mask patterns and said ion-implantation buffer layers as an etching mask, thereby forming a second recess;
• implanting ions into said semiconductor substrate around said first and second recesses, wherein the ions are implanted obliquely;
• and
• forming an insulating layer on the resulting structure and etching back said insulating layer so that said first and second recesses are fully filled with said insulating layer.

A semiconductor device having a shallow trench isolation structure comprising:

• a semiconductor substrate having a trench, wherein the upper part of said trench is broader than the lower part of said trench;
• a first insulating layer formed on the sidewalls of said upper part of said trench;
• a second insulating layer buried in said trench for isolation of said semiconductor devices;
• and
• low-concentration doped regions formed in said semiconductor device, wherein said low-concentration doped regions are near said upper part of said trench;
• and
• high-concentration doped regions formed in said semiconductor device, wherein said high-concentration doped regions are near said lower part of said trench.