Method of manufacturing a device in a silicon wafer

Abstract

A silicon body (10) of a first conductivity type is covered with a sandwich of silicon dioxide (12), polycrystalline silicon (14) and silicon nitride (16). Source, drain, and interconnect work sites of the body are exposed by a first photoshaping operation. The work sites are doped forming regions (21, 22, 23) of a second conductivity type. Silicon dioxide (24, 26, 28) is grown over the work sites. A second photoshaping operation provides an opening 36. The walls of the opening 36 on two opposite sides comprise sides of the sandwich layer as established by the first photoshaping operation and the two remaining walls comprise sides of the silicon dioxide as established by the second photoshaping operation. Silicon nitride (44) is next deposited over the entire wafer (15) which is then photoshaped to define the field regions (46, 48). The etching process is continued to remove part of the silicon body as well as the sides of those exposed regions. Thereafter, silicon dioxide (47, 49) is grown in the field regions. The remaining silicon nitride layer is removed to reveal the underlying conductive polycrystalline silicon (14) at the gate region, the walls of the contact opening 36 and the interconnect region 23. A conductive material (51, 50) is deposited over the wafer (15) and then photoshaped to provide the desired pattern of ohmic interconnections.