Gate-all-around field effect transistor structures and methods

摘要

Disclosed are gate-all-around (GAA) field effect transistors (FETs) and methods of forming them. In one GAAFET, a semiconductor body is on an insulator layer. A gate wraps around the semiconductor body (i.e., is adjacent to the top, bottom and opposing sides of the semiconductor body) at a channel region with a lower portion of the gate being in a cavity in the insulator layer. In another GAAFET, multiple semiconductor bodies are on an insulator layer. A gate wraps around and extends between the semiconductor bodies at channel regions with a lower portion of the gate being contained in a cavity in the insulator layer. To reduce gate resistance and gate-to-source/drain contact capacitance, the lower portion extends a greater distance below the bottom(s) of the semiconductor body(ies) than the upper portion extends above the top(s). To further reduce gate resistance, the length and width of the lower portion increases from the top surface of the insulator layer downward.

主权项

1. A field effect transistor comprising:
an insulator layer having a top surface and a cavity at said top surface; a semiconductor body on said top surface, said semiconductor body having a bottom, a top opposite said bottom and opposing sides, said semiconductor body comprising source/drain regions and a channel region positioned laterally between said source/drain regions, and said semiconductor body traversing said cavity such that said channel region is aligned above said cavity; and, a gate having a lower portion within said cavity adjacent to said bottom of said semiconductor body at said channel region and an upper portion adjacent to said top and said opposing sides of said semiconductor body at said channel region, said lower portion extending a first distance below said bottom of said semiconductor body, said upper portion extending a second distance above said top of said semiconductor body, and said second distance being less than said first distance.