Buried power rail and method forming same

A method of forming an integrated circuit structure, the method comprising:

• etching a semiconductor substrate to form two semiconductor strips, wherein the two semiconductor strips are over a bulk portion of the semiconductor substrate;
• etching the bulk portion to form a trench in the bulk portion of the semiconductor substrate, wherein the trench comprises a first portion laterally between the two semiconductor strips, and second portions overlapped by the two semiconductor strips;
• forming a liner dielectric layer lining the trench;
• forming a buried contact in the trench;
• forming a buried power rail over and connected to the buried contact, wherein the buried power rail is between the two semiconductor strips;
• and
• forming isolation regions on opposite sides of the two semiconductor strips, wherein the buried power rail is underlying a portion of the isolation regions.

A method of forming an integrated circuit structure, the method comprising:

• etching a semiconductor substrate from a front side to form two semiconductor strips, wherein the two semiconductor strips are over a bulk portion of the semiconductor substrate;
• etching the bulk portion to form a trench in the bulk portion of the semiconductor substrate;
• forming a liner dielectric layer lining the trench;
• depositing a buried contact in the trench;
• forming a buried power rail over and connected to the buried contact, wherein the buried power rail is between the two semiconductor strips;
• forming isolation regions on opposite sides of the two semiconductor strips, wherein the buried power rail is underlying a portion of the isolation regions;
• and
• forming a contact plug from a backside of the semiconductor substrate, wherein the contact plug is electrically connected to the buried contact.