Patent ID: 11862707
Assignee: STMICROELECTRONICS S.R.L.
Field: Semiconductors (Electrical engineering)
Classification: CPC H | IPC H

Claim 7:
8. A normally off heterostructure field-effect transistor (HEMT), comprising:
a semiconductor heterostructure including:
a first semiconductor layer; and
a second semiconductor layer on the first semiconductor layer;

a passivation layer of dielectric material on the semiconductor heterostructure;
a trench extending entirely through the passivation layer, entirely through the second semiconductor layer, and partially through the first semiconductor layer, the trench including:
a bottom surface;
a planar first sidewall extending entirely through the second semiconductor layer; and
a plurality of steps, each step including a horizontal surface higher in the trench than the bottom surface and a vertical surface laterally opposite the first sidewall on a second side of the trench in the second semiconductor layer;

a dielectric layer coating the first sidewall and the plurality of steps;
a conductive gate on the dielectric layer and filling the trench; and
a source metalization extending through the passivation layer and in contact with the second semiconductor layer.