Semiconductor substrate, semiconductor device, and semiconductor substrate manufacturing method

Abstract

An electric device formed in a semiconductor layer on the front side can be easily designed when a thick portion, e.g., an optical waveguide, is fabricated in a semiconductor layer interposed between two insulating layers. Double SOI substrate (10) is composed of, from the front side, a silicon layer (15), an insulating film (silicon oxide film) (14), a silicon layer (13), and an insulating layer (12). The depth distribution of the upper insulating layer (14) is uniform, and that of the lower insulating layer (12) is ununiform. A thick portion along a predetermined path is formed. The refractive index of silicon is 3.5, and that of SiO2 is 1.5. The thick portion of the silicon layer (13) serves as a core. The insulating layers (12, 14) corresponding to the thick portion serves as clads. Thus, an optical waveguide (16) along a predetermined path is formed. The thickness of the silicon layer (15) on the front side is uniform, and thereby the characteristics of MOS devices fabricated in regions of the silicon layer (13) can be easily equalized, and the design of whole electric devices can be facilitated.

Description

technical field [0001] The present invention relates to a semiconductor substrate having a semiconductor layer on an insulator layer, a semiconductor device using the semiconductor substrate, and a method of manufacturing the semiconductor substrate. More specifically, the present invention relates to a semiconductor substrate and the like, the semiconductor substrate having a configuration in which a first insulator layer and a second insulator layer are formed in this order from the surface side near the surface, the first insulator layer has a uniform depth distribution; the semiconductor layer sandwiched between the first and second insulator layers has a thick portion at predetermined positions so that when the semiconductor layer sandwiched between the two insulator layers forms the thick portion Design of electronic devices formed on the surface side. Background technique [0002] The prior art proposes to form an optical waveguide on a silicon-on-insulator (SOI) sub...

AI Technical Summary

Problems solved by technology

[0010] However, in the dual structure SOI substrate 50, the upper insulating film 54 has an uneven depth distribution, so that the surface side silicon layer 55 has an uneven thickness.

Therefore, when forming, for example, a MOS device on the silicon layer 55, it is difficult to make the characteristics of the MOS formed on the thin portion of the silicon layer 55 corresponding to the optical waveguide 56 the same as that of the thick portion of the silicon layer 55 not corresponding to the optical waveguide 56. characteristics of MOS devices formed on

In addition, mixing various MOS devices with different characteristics increases the overall complexity of designing electronic devices