Abstract: According to one embodiment, a semiconductor device includes: a substrate in which, on a semiconductor substrate of a first conductivity type, a buried layer of a second conductivity type and a semiconductor layer of the second conductivity type are stacked; trench that define an element forming region in the substrate; element isolation insulation film formed in the trench; and a semiconductor element formed in the element forming region. The trench include first trench formed from the surface of the substrate to boundary depth and second trench formed from the boundary depth to the bottom and having a diameter smaller than that of the first trench. First diffusion layers connected to the buried layer are formed around the first or second trench according to inter-element breakdown voltage required of the semiconductor element.

Abstract: According to one embodiment, a semiconductor device includes: a substrate in which, on a semiconductor substrate of a first conductivity type, a buried layer of a second conductivity type and a semiconductor layer of the second conductivity type are stacked; trench that define an element forming region in the substrate; element isolation insulation film formed in the trench; and a semiconductor element formed in the element forming region. The trench include first trench formed from the surface of the substrate to boundary depth and second trench formed from the boundary depth to the bottom and having a diameter smaller than that of the first trench. First diffusion layers connected to the buried layer are formed around the first or second trench according to inter-element breakdown voltage required of the semiconductor element.

Abstract: A plurality of cells are provided in a concave portion of a top plate. A cloth to which water is penetrated is provided in a back face of each cell, and a wafer is attracted by the cloth. First and second pipes are connected to each cell. The first pipe introduces liquid to the cell, and the second pipe discharges liquid from the cell, and guides liquid to the first pipe. A constant-temperature device is provided to each first pipe, and a temperature of liquid of each cell is adjusted by the constant-temperature device in accordance with a temperature distribution of the wafer. Whereby, a polishing rate of each part of the wafer can be equalized.