SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To provide a semiconductor device including an SOI substrate, which has a long creepage distance on a top edge side of an opening formed in an active layer without an increase in size to achieve improved withstand voltage.SOLUTION: A semiconductor device 100 comprises: an SOI substrate 10 in which a support substrate 12, an embedded insulation layer 14 and an active layer 16 are laminated; a first insulation film 20; a second insulation film 30; an interlayer insulation film 40; a trench 50 which pierces the second insulation film 30, the first insulation film 20 and the active layer 16 and has a cavity inside and has a top edge blocked by the interlayer insulation film 40; and a first side etching region 52 which is provided in the first insulation film 20 and lies adjacent to the trench 50 and has a cavity inside, which contacts the cavity inside the trench 50. The second insulation film 30 has an etching selectivity higher than that of the first insulation film 20. An opening width W1 of the first insulation film 20 is wider than an opening width Wa of the active layer 16 and wider than an opening width W2 of the second insulation film 30.SELECTED DRAWING: Figure 1 【課題】ＳＯＩ基板を備える半導体装置であって、大型化することなく、活性層に設けられた開口部の上端側の沿面距離が長く、絶縁耐圧が向上した半導体装置を提供する。【解決手段】支持基板１２、埋込絶縁層１４および活性層１６が積層されているＳＯＩ基板１０と、第１の絶縁膜２０と、第２の絶縁膜３０と、層間絶縁膜４０と、第２の絶縁膜３０、第１の絶縁膜２０および活性層１６を貫通し、内部に空洞を有し、層間絶縁膜４０によって上端部が閉塞されているトレンチ５０と、第１の絶縁膜２０に設けられ、トレンチ５０と隣接し、内部にトレンチ５０内部の空洞と接する空洞を有する第１のサイドエッチング領域５２と、を備える半導体装置１００であって、第２の絶縁膜３０は第１の絶縁膜２０に対してエッチング選択比が高く、第１の絶縁膜２０の開口幅Ｗ１が、活性層１６の開口幅Ｗａよりも広く、且つ第２の絶縁膜３０の開口幅Ｗ２よりも広いことを特徴とする。【選択図】図１