Patent ID: 7816257

Claim:
A method of forming an integrated circuit device, the method comprising: forming a first insulating layer on a substrate; forming a semiconductor layer comprising single crystalline silicon on the first insulating layer; forming a second insulating layer on the semiconductor layer; forming an opening extending through the first and second insulating layers and through the semiconductor layer between the first insulating layer and the second insulating layer to a surface of the substrate, the opening including a recess between the first and second insulating layers adjacent the semiconductor layer; and forming a conductive plug comprising a plurality of stacked metal layers in the opening to contact the substrate and a side of the semiconductor layer; wherein forming the opening further comprises selectively recessing a portion of the semiconductor layer at a sidewall of the opening to form the recess between the first and second insulating layers and to define a recessed portion of the semiconductor layer, and wherein forming the conductive plug comprises: forming a first conductive layer on the sidewall of the opening and on the surface of the substrate and laterally extending into the recess between the first and second insulating layers to contact the recessed portion of the semiconductor layer, wherein the first conductive layer has a greater thickness in the recess between the first and second insulating layers than a thickness on the sidewall of the opening; forming a buffer layer on the first conductive layer on the sidewall of the opening and on the surface of the substrate; and forming a second conductive layer on the buffer layer so as to substantially fill the opening with the second conductive layer, wherein the first and the second conductive layers respectively comprise first and second metal layers and the buffer layer comprises a metal nitride layer, wherein the first metal layer fills the recess, and wherein the first metal layer comprises an ohmic layer between the semiconductor layer and the substrate.