Formation of isolation surrounding well implantation

A method comprising:

• providing a semiconductor substrate;
• forming a hard-mask layer on top of the substrate;
• forming a first resist-mask on top of a first portion of the hard-mask layer
• etching a top portion of the hard-mask layer in areas not covered by the first resist-mask to create a recessed portion of the hard-mask layer;
• applying the first resist-mask in forming a first type of wells in a first region of the substrate;
• forming a second resist-mask on top of a second portion of the hard-mask layer wherein a first portion of the recessed portion of the hard-mask layer is covered by the second resist-mask;
• etching a second portion of the recessed portion of the hard-mask layer that is not covered by the second resist-mask until the substrate is exposed;
• applying the second resist-mask in forming a second type of wells in a second region of the substrate;
• etching at least the exposed portion of the substrate to create deep trenches that separate the first type of wells from the second types of wells;
• and
• filling the deep trenches with insulating materials.