A semiconductor device and a method of forming the same are provided. The semiconductor device includes a gate stack over an active region and a source/drain region in the active region adjacent the gate stack. The source/drain region includes a first semiconductor layer having a first germanium concentration and a second semiconductor layer over the first semiconductor layer. The second semiconductor layer has a second germanium concentration greater than the first germanium concentration. The source/drain region further includes a third semiconductor layer over the second semiconductor layer and a fourth semiconductor layer over the third semiconductor layer. The third semiconductor layer has a third germanium concentration greater than the second germanium concentration. The fourth semiconductor layer has a fourth germanium concentration less than the third germanium concentration.

A semiconductor device and a method of forming the same are provided. The semiconductor device includes a gate stack over an active region and a source/drain region in the active region adjacent the gate stack. The source/drain region includes a first semiconductor layer having a first germanium concentration and a second semiconductor layer over the first semiconductor layer. The second semiconductor layer has a second germanium concentration greater than the first germanium concentration. The source/drain region further includes a third semiconductor layer over the second semiconductor layer and a fourth semiconductor layer over the third semiconductor layer. The third semiconductor layer has a third germanium concentration greater than the second germanium concentration. The fourth semiconductor layer has a fourth germanium concentration less than the third germanium concentration.

A bipolar junction transistor is provided with an emitter structure that is positioned above the upper surface of the base region. The thickness of the emitter and the interfacial oxide thickness between the emitter and the base is configured to optimize a gain for a given type of transistor. A method of fabricating PNP and NPN transistors on the same substrate using a complementary bipolar fabrication process is provided. The method enables the emitter structure for the NPN transistor to be defined separately to that of the PNP transistor. This is achieved by epitaxially growing the emitter layer for the PNP transistor and growing the emitter layer for the NPN transistor in a thermal furnace.

A semiconductor device includes a substrate, a device isolation layer on the substrate, the device isolation layer defining a first active pattern, a pair of first source/drain patterns on the first active pattern, the pair of first source/drain patterns being spaced apart from each other in a first direction, and each of the pair of first source/drain patterns having a maximum first width in the first direction, a first channel pattern between the pair of first source/drain patterns, a gate electrode on the first channel pattern and extends in a second direction intersecting the first direction, and a first amorphous region in the first active pattern, the first amorphous region being below at least one of the pair of first source/drain patterns, and having a maximum second width in the first direction that is less than the maximum first width.

A semiconductor device includes a substrate, a device isolation layer on the substrate, the device isolation layer defining a first active pattern, a pair of first source/drain patterns on the first active pattern, the pair of first source/drain patterns being spaced apart from each other in a first direction, and each of the pair of first source/drain patterns having a maximum first width in the first direction, a first channel pattern between the pair of first source/drain patterns, a gate electrode on the first channel pattern and extends in a second direction intersecting the first direction, and a first amorphous region in the first active pattern, the first amorphous region being below at least one of the pair of first source/drain patterns, and having a maximum second width in the first direction that is less than the maximum first width.

Semiconductor device structures having low-k features and methods of forming low-k features are described herein. Some examples relate to a surface modification layer, which may protect a low-k feature during subsequent processing. Some examples relate to gate spacers that include a low-k feature. Some examples relate to a low-k contact etch stop layer. Example methods are described for forming such features.

A semiconductor device includes a core insulating layer extending in a first direction, an etch stop layer disposed on the core insulating layer, a channel layer extending along a sidewall of the core insulating layer and a sidewall of the etch stop layer, conductive patterns each surrounding the channel layer and stacked to be spaced apart from each other in the first direction, and an impurity region formed in an upper end of the channel layer.

A semiconductor device includes a core insulating layer extending in a first direction, an etch stop layer disposed on the core insulating layer, a channel layer extending along a sidewall of the core insulating layer and a sidewall of the etch stop layer, conductive patterns each surrounding the channel layer and stacked to be spaced apart from each other in the first direction, and an impurity region formed in an upper end of the channel layer.

Exemplary methods of forming a semiconductor structure may include forming a doped silicon layer on a semiconductor substrate. A level of doping may be increased at an increasing distance from the semiconductor substrate. The methods may include etching the doped silicon layer to define a trench extending to the semiconductor substrate. The doped silicon layer may define a sloping sidewall of the trench. The trench may be characterized by a depth of greater than or about 30 μm. The methods may include lining the trench with a first oxide material. The methods may include depositing a second oxide material within the trench. The methods may include forming a contact to produce a power device.

Exemplary methods of forming a semiconductor structure may include forming a doped silicon layer on a semiconductor substrate. A level of doping may be increased at an increasing distance from the semiconductor substrate. The methods may include etching the doped silicon layer to define a trench extending to the semiconductor substrate. The doped silicon layer may define a sloping sidewall of the trench. The trench may be characterized by a depth of greater than or about 30 μm. The methods may include lining the trench with a first oxide material. The methods may include depositing a second oxide material within the trench. The methods may include forming a contact to produce a power device.