Semiconductor devices with strained source/drain structures

摘要

An integrated circuit device and method for manufacturing the integrated circuit device is disclosed. The disclosed method provides a processing for forming improved source/drain features in the semiconductor device. Semiconductor devices with the improved source/drain features may prevent or reduce defects and achieve high strain effect resulting from epi layers. In an embodiment, the source/drain features comprises a second portion surrounding a first portion, and a third portion between the second portion and the semiconductor substrate, wherein the second portion has a composition different from the first and third portions.

主权项

1. A device, comprising:
a semiconductor substrate; a gate structure over the semiconductor substrate; spacers overlying opposite sidewalls of the gate structure; lightly doped source/drain (LDD) regions in the semiconductor substrate, interposed by the gate structure; source/drain (S/D) regions in the semiconductor substrate, adjacent to the LDD regions and partially under the spacers, wherein each of the S/D regions comprises:
a first portion adjacent to a top surface of the semiconductor substrate;a second portion surrounding the first portion; anda third portion between the second portion and the semiconductor substrate, wherein the second portion has a composition different from the first and third portions; and contact features over the S/D regions, wherein the first, second, and third portions are formed in a trench of the semiconductor substrate, the trench comprises:
a first sidewall section extending obliquely downward from the top surface of the semiconductor substrate and away from a center of the trench,a second sidewall section further extending obliquely downward from the first sidewall section and toward the center of the trench, anda bottom connected to the second sidewall section, and the third portion includes:
an upper part included in a tip portion of the trench, the tip portion defined by the first and second sidewall sections, anda lower part on the bottom of the trench, the lower part physically discontinuous from the upper part.