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

Claim 9:
10. 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 first step on a first side of the trench, the first step having a horizontal surface higher in the trench than the bottom surface;
a plurality of second steps on a second side of the trench each having a respective horizontal surface higher in the trench than the bottom surface;

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