Semiconductor devices and methods of forming thereof are disclosed. A substrate with different device regions defined in the substrate is provided. A deep trench isolation (DTI) structure is formed in the substrate to isolate the different device regions. The DTI structure includes a fill material and a dielectric layer surrounding the fill material in the DTI structure. Local oxidation of the substrate is performed over the DTI structure to form a thermal dielectric layer which overlaps the DTI structure. The thermal dielectric layer which overlaps the DTI structure forms a thick top corner dielectric in the DTI structure.

A high voltage device includes: a semiconductor layer, a well, a bulk region, a gate, a source, and a drain. The bulk region is formed in the semiconductor layer and contacts the well region along a channel direction. A portion of the bulk region is vertically below and in contact with the gate, to provide an inversion region of the high voltage device when the high voltage device is in conductive operation. A portion of the well lies between the bulk region and the drain, to separate the bulk region from the drain. A first concentration peak region of an impurities doping profile of the bulk region is vertically below and in contact with the source. A concentration of a second conductivity type impurities of the first concentration peak region is higher than that of other regions in the bulk region.

A high voltage device includes: a semiconductor layer, a well, a bulk region, a gate, a source, and a drain. The bulk region is formed in the semiconductor layer and contacts the well region along a channel direction. A portion of the bulk region is vertically below and in contact with the gate, to provide an inversion region of the high voltage device when the high voltage device is in conductive operation. A portion of the well lies between the bulk region and the drain, to separate the bulk region from the drain. A first concentration peak region of an impurities doping profile of the bulk region is vertically below and in contact with the source. A concentration of a second conductivity type impurities of the first concentration peak region is higher than that of other regions in the bulk region.

A method of fabrication of alignment marks for a non-STI CMOS image sensor is introduced. In some embodiments, zero layer alignment marks and active are alignment marks may be simultaneously formed on a wafer. A substrate of the wafer may be patterned to form one or more recesses in the substrate. The recesses may be filled with a dielectric material using, for example, a field oxidation method and/or suitable deposition methods. Structures formed by the above process may correspond to elements of the zero layer alignment marks and/or to elements the active area alignment marks.

A semiconductor device including a substrate and a shallow trench isolation (STI) structure is provided. The substrate has a first voltage area and a second voltage area. A top surface of the substrate in the second voltage area is higher than a top surface of the substrate in the first voltage area, and a trench is defined in the substrate in between the first and second voltage area. The STI structure is located in the substrate within the trench, wherein a first portion of the STI structure is located in the first voltage area, a second portion of the STI structure is located in the second voltage area, and a step height difference exist in between a bottom surface of the first portion of the STI structure in the first voltage area and a bottom surface of the second portion of the STI structure in the second voltage area.

A method of forming a semiconductor device is provided including the following steps. A substrate having a first voltage area and a second voltage area is provided. A first oxide layer is formed in the first voltage area. The first oxide layer is removed to form a recess in the first voltage area. A shallow trench isolation (STI) structure is formed in the substrate, wherein a first portion of the STI structure is located in the first voltage area and a second portion of the STI structure is located in the second voltage area, a top surface of the STI structure is higher than the top surface of the substrate, and a bottom surface of the first portion of the STI structure in the first voltage area is lower than a bottom surface of the second portion of the STI structure in the second voltage area.

A method of forming a semiconductor device is provided including the following steps. A substrate having a first voltage area and a second voltage area is provided. A first oxide layer is formed in the first voltage area. The first oxide layer is removed to form a recess in the first voltage area. A shallow trench isolation (STI) structure is formed in the substrate, wherein a first portion of the STI structure is located in the first voltage area and a second portion of the STI structure is located in the second voltage area, a top surface of the STI structure is higher than the top surface of the substrate, and a bottom surface of the first portion of the STI structure in the first voltage area is lower than a bottom surface of the second portion of the STI structure in the second voltage area.

A method of a forming semiconductor fin structures that includes forming a plurality of fin structures with a first etch to a first depth in a substrate. The plurality of fin structures have a first width to the first depth. A spacer is formed on sidewalls of the plurality of fin structures. A second etch step can then extend the plurality of fin structures to a second depth with a second etch. The plurality of fin structures have a second width greater than the first width at the second depth portion. At least a portion of the trench separating adjacent fin structures may then be filled with a dielectric formed by an oxidation process. The portion of the fin structures extending above the dielectric fill is the active region of the fin structures which has a uniform height for all of the fin structure in the plurality of fin structures.

A method for fabricating a semiconductor device includes forming an opening in a first epitaxial lateral overgrowth region to expose a surface of the semiconductor substrate within the opening. The method further includes forming an insulation region at the exposed surface of the semiconductor substrate within the opening and filling the opening with a second semiconductor material to form a second epitaxial lateral overgrowth region using a lateral epitaxial growth process.

A method of fabrication of alignment marks for a non-STI CMOS image sensor is introduced. In some embodiments, zero layer alignment marks and active are alignment marks may be simultaneously formed on a wafer. A substrate of the wafer may be patterned to form one or more recesses in the substrate. The recesses may be filled with a dielectric material using, for example, a field oxidation method and/or suitable deposition methods. Structures formed by the above process may correspond to elements of the zero layer alignment marks and/or to elements the active area alignment marks.