Semiconductor device

Abstract

A semiconductor device comprises: a semiconductor layer; a first conductivity type first impurity region; a second conductivity type body region; a first conductivity type second impurity region; a field insulating film; a gate insulating film; a first floating plate provided in the form of a ring having a constant width on the field insulating film; and a second floating plate provided in the form of a ring having a constant width on the same layer above the first floating plate, wherein the first floating plate and the second floating plate are formed by not less than three in total so that the peripheral lengths at the centers in the width direction thereof are entirely different from one another, alternately arranged in plan view so that the one having a relatively smaller peripheral length is stored in an inner region of the one having a relatively larger peripheral length, and formed to satisfy the relational expression: L / d=constant (L: the outer periphery of the inner one of the first and second floating plates adjacent to each other in plan view, d: the distance between the outer periphery of the plate defining L and the inner periphery of the first or second floating plate adjacent to the plate to be opposed to the outer periphery thereof).

Description

technical field [0001] The present invention relates to a semiconductor device. Background technique [0002] Conventionally, LDMOSFETs are known as high withstand voltage elements used in power MOSFETs. [0003] Figure 10 It is a schematic cross-sectional view of a semiconductor device including a conventional LDMOSFET. [0004] The semiconductor device 101 includes a thick-film SOI substrate 102 . The thick-film SOI substrate 102 has a structure in which a N - type active layer 105 is laminated. [0005] In the active layer 105 , a deep groove 106 is formed penetratingly in the layer thickness direction, and the depth is from the surface of the active layer 105 to the BOX layer 104 . The inner surface of the deep groove 106 is covered with a silicon oxide film 107 . [0006] The inside of silicon oxide film 107 is filled with polysilicon 108 . As a result, an element formation region 109 is formed on the active layer 105, surrounded by the deep groove 106, and insul...

AI Technical Summary

Problems solved by technology

Therefore, in the above-mentioned structure, although the capacity corresponding to the unit length in the circumferential direction of the floating plate can be made the same in each capacitor, the total capacity of the capacitor cannot be made the same.

As a result, the potentials between the opposing electrodes of each capacitor are actually different, and the potential distribution in the drift region 112 cannot be made uniform.

Images