Method for a controlled bottle trench for a dram storage node

A method for fabricating a trench for a semiconductor device, comprising the steps of:

• a) providing a substrate;
• b) forming a plurality of insulating layers on said substrate;
• c) forming a deep trench region upper portion having side walls in said layered substrate, and a width;
• d) forming a lower portion in said trench region having side walls, a bottom, and a width;
• e) forming a first impurity diffusion region along said lower portion of said trench region, said impurity diffusion region being tightly controlled by temperature and time of diffusion;
• f) performing an isotropic wet etch to widen said width of said lower portion of said trench region, such that removal of material of said substrate to widen said width of said lower portion comprises removing said material from the side walls of said lower portion;
• g) forming a buried plate region on a portion of said side walls of said trench region;
• and,
• h) forming an insulating layer on said lower portion and said side walls of said trench region.

A method for fabricating a semiconductor device with a controlled bottle trench capacitor, comprising the steps of:

• a) providing a substrate;
• b) layering said substrate and using said layers as a deep trench mask;
• c) removing material from said substrate to form a deep trench within said layered substrate;
• d) forming protective layers on a portion of the side walls of said trenches;
• e) resuming removal of material from said substrate deep trench below said protective layers;
• f) exposing said side wall substrate in said trenches unprotected by said protective layers;
• g) depositing a first dopant source material covering at least a portion of said side wall substrate;
• h) diffusing at least some of a first dopant material into said exposed side wall substrate in said trenches, said diffusing being tightly controlled by temperature and time;
• i) widening said trench by removing at least a portion of said first dopant source material and a portion of said substrate doped by said first dopant in said exposed side wall substrate in said trenches to form said bottle trench, such that removal of material of said layered substrate to widen said width of said exposed side wall substrate of said trench comprises removing said material from the side walls of said trench unprotected by said protective layers;
• j) depositing a second dopant source material and implanting a second dopant at least on a portion of said side walls of said trenches uncovered by said protective layers including diffusing said second dopant into said substrate to form a buried plate region;
• k) forming an insulating layer on the lower portion and side walls of said trenches;
• and,
• l) forming a capacitor by filling said bottle trench with a node conductor.