Method of forming closely spaced device regions utilizing selective etching and diffusion

A method for forming a semiconductor structure comprising the steps of:

• (a) providing a semiconductor having a first conductivity type;
• (b) forming an isolation region having an insulating material in a portion of the semiconductor;
• (c) forming a doped region in the semiconductor having a portion thereof contiguous to the isolation region, such doped region being formed with a conductivity type opposite the first conductivity type;
• (d) bringing an etchant into contact with a surface portion of the doped region and a contiguous surface portion of the isolation region;
• and
• (e) selectively etching the doped region forming a depression with converging side wall portions separated from the isolation region by portions of the doped region.

A method for forming a semiconductor structure comprising the steps of:

• (a) providing an isolation region having an insulating material in a semiconductor body;
• (b) forming a doped region in such semiconductor body, a portion of such doped region being contiguous to a portion of the isolation region;
• and
• (c) forming a depression in the doped region with upper side wall portions in contact with portions of the insulating material and lower side wall portions separated from an adjacent portion of the insulating material of the isolation region by a portion of the doped region.

A method for forming a semiconductor device comprising the steps of:

• (a) providing an isolation region having an insulating material in a doped semiconductor body;
• (b) forming an oppositely doped region in such semiconductor with a portion of such doped region being formed adjacent a portion of the isolation region;
• (c) forming a depression in the doped region with converging side walls separated from adjacent portions of the isolation region by a portion of the doped region;
• (d) subsequently forming a second doped region in the semiconductor body beneath bottom portions of the depression, such second doped region being of the same type dopant as the first-mentioned doped region and of lesser doping concentration than such first-mentioned doped region;
• and
• (e) providing an electrical contact to the second doped region.

The method of forming a transistor comprising the steps of:

• (a) forming a doped epitaxial layer on a substrate;
• (b) forming an isolation region having an insulating material in a portion of the epitaxial layer;
• (c) forming a first doped region in the epitaxial layer with a conductivity type opposite that of the epitaxial layer, such first doped region having a portion thereof adjacent the isolation region;
• (d) forming a depression in the doped region having a side wall separated from portions of the isolation region by portions of the first doped region;
• (e) subsequently forming a second doped region of conductivity type like that of the first doped region in the epitaxial layer beneath a bottom portion of the depression;
• and
• (f) forming an emitter contact on the bottom of the depression in contact with the second doped region, a base electrode in contact with the first doped region, and a collector contact in contact with the epitaxial layer.

A method for forming a semiconductor structure comprising the steps of:

• (a) forming a first doped region in a portion of a semiconductor, such first doped region having a first doping concentration;
• (b) forming a depression in the semiconductor with side wall portions passing through the first doped region into the semiconductor and a bottom wall portion disposed in the semiconductor;
• (c) increasing the size of the first doped region so that edge portions of such region extend under the bottom wall portion of the depression;
• and
• (d) forming a second doped region in the semiconductor under the bottom wall portion of the depression, end portions of such doped region extending into the edge portions of first doped region electrically connecting the first and second doped regions, such second doped region having a doping concentration less than the first doping concentration.