Optimized contact structure

A method of fabricating a semiconductor die, the method comprising:

• providing a substrate;
• and
• creating a contact at least partially embedded within the substrate, the contact comprising:
• a first portion with a first vertical cross-section having a first cross-sectional area, the first vertical cross-section having a first width and a first height;
• and
• a second portion with a second vertical cross-section having a second cross-sectional area less than the first cross-sectional area, the second vertical cross-section comprising:
• a lower portion having the first width and a second height less than the first height;
• and
• an upper portion disposed above the lower portion and having a second width less than the first width, and having a third height less than the first height.

A method of fabricating a contact within a semiconductor die, the method comprising:

• creating, within a substrate, a contact hole having a first width, a first length, and a first depth;
• depositing, within the contact hole, an electrically conducting material to form the contact having the first width and the first length;
• protecting a first portion of the contact from etching;
• vertically etching a second portion of the contact to create a recess having the first width, a second length less than the first length, and a second depth less than the first depth such that the second portion of the contact has the first width and a first height;
• depositing, with the recess, a conformal spacing material having a thickness T;
• anisotropically etching the conformal spacing material to a depth=T to expose at least some of the second portion of the contact;
• selectively depositing additional electrically conducting material onto the second portion of the contact up to a third depth less than the second depth, forming an upper portion of the second portion of the contact having a second width and a third length less than the second length, a lower portion of the second portion of the contact having the first width and the first height;
• and
• removing the conformal spacing material to create a gap between outer surfaces of the upper portion of the second portion of the contact and inner surfaces of the recess.