Method of manufacturing semiconductor device having elements isolated by trench

A method of manufacturing a semiconductor device comprising the steps of:

• anisotropic etching a monocrystalline silicon substrate to form a plurality of trenches therein each having a width of 0.8 to 1.6 .mu.m and surrounding each of a plurality of element forming regions wherein a bipolar transistor is formed, said trenches being positioned at intervals of approximately 2.4 .mu.m;
• forming a nonoxide film on said element forming regions with an interval between an end portion of said nonoxide film and a side wall of each said trench at a side thereof near said element forming regions of said trenches being approximately 1.6 .mu.m;
• forming an oxide film having a film thickness no greater than 7,200 .ANG. on a surface of said substrate including an inside portion of each of said trenches using said nonoxide film as a mask, with each of said trenches not being completely filled by said oxide film;
• completely filling said trenches with a polysilicon layer having an exposed portion;
• and
• oxidizing said exposed portion of said polysilicon layer.

A method of manufacturing a semiconductor device comprising the steps of:

• anisotropic etching a monocrystalline silicon substrate to form a plurality of trenches therein each having a width of 0.7 to 1.4 .mu.m and surrounding each of a plurality of element forming regions wherein a bipolar transistor is formed, said trenches being positioned at intervals of approximately 2.1 .mu.m;
• forming a nonoxide film on said element forming regions with an interval between an end portion of said nonoxide film and a side wall of each said trenches at a side thereof near said element forming regions of said trenches being approximately 1.4 .mu.m;
• forming an oxide film having a film thickness no greater than 6,300 .ANG. on a surface of said substrate including an inside portion of each of said trenches using said nonoxide film as a mask, with each of said trenches not being completely filled by said oxide film;
• completely filling said trenches with a polysilicon layer having an exposed portion;
• and
• oxidizing said exposed portion of said polysilicon layer.