Deep trench with self-aligned sinker

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

• providing a substrate comprising semiconductor material;
• forming a buried layer in the substrate so that the buried layer has a first conductivity type and a top surface of the buried layer is at least 2 microns below a top surface of the substrate;
• forming a partial deep trench less than 6 microns wide in the substrate extending down to the buried layer, so that the partial deep trench does not extend below a bottom surface of the buried layer;
• implanting dopants into the substrate along sidewalls of the partial deep trench to form a sinker implanted layer extending down to the buried layer, the sinker implanted layer having the first conductivity type;
• removing material from the substrate so as to extend the partial deep trench below the bottom surface of the buried layer to form a deep trench;
• forming a dielectric liner in the deep trench on sidewalls of the deep trench, contacting the substrate;
• and
• activating the dopants in the sinker implanted layer to form a self-aligned sinker having the first conductivity type disposed in the substrate and abutting the deep trench structure, extending down to the buried layer, and extending laterally from the deep trench structures by a thickness of less than 2.5 microns.