Contact plug and method of formation

A semiconductor device, comprising:

• a dielectric stack formed on a substrate;
• a contact region formed within the dielectric stack and extending into the substrate, the contact region having side portions and a bottom portion;
• a dielectric barrier layer formed on the side portions of the contact region;
• a conductive blocking layer formed along the side portions of the contact region over the dielectric barrier layer and the dielectric stack, wherein a topmost surface of the dielectric barrier layer is lower than a topmost surface of the conductive blocking layer, and the topmost surface of the conductive blocking layer is substantially level with a top surface of the dielectric stack, and a bottommost surface of the dielectric barrier layer is substantially level with a bottommost surface of the conductive blocking layer, and wherein the conductive blocking layer has a lateral surface lower than the top surface of the dielectric stack and higher than the topmost surface of the dielectric barrier layer;
• a conductive layer formed along the side portions and bottom portion of the contact region over the conductive blocking layer in the contact region;
• a conductive barrier layer formed on the conductive layer in the contact region, wherein a bottom surface of the conductive blocking layer is substantially level with a top surface of the substrate, and the conductive layer and the conductive barrier layer extend into the substrate;
• a conduct core over the conductive barrier layer in the contact region;
• and
• a silicide region located in the substrate beneath the conductive layer.

A method for forming a semiconductor contact plug, the method comprising:

• depositing a dielectric stack over a substrate;
• forming a contact region in the dielectric stack, the contact region extending into the substrate and having side portions and a bottom portion that exposes the substrate;
• forming a dielectric barrier layer along the side portions of the contact region;
• depositing a first metal layer in the contact region over the dielectric barrier layer and the dielectric stack to cover the side portions and bottom portion of the contact region, wherein the first metal layer has a lateral surface lower than a top surface of the dielectric stack and higher than a topmost surface of the dielectric barrier layer;
• depositing a second metal layer over the first metal layer;
• depositing a conductive barrier layer over the second metal layer;
• and
• performing a first annealing process to form a silicide region in the substrate;
• and
• performing a second annealing process by diffusing a portion of the second metal layer into the substrate to increase a thickness of the silicide region in the substrate, wherein the first annealing process is performed before the formation of the conductive barrier layer, and the second annealing process is performed after the formation of the conductive barrier layer.