This embodiment differs from the first embodiment in that, in the first embodiment, the drift oxide region 24 is a LOCOS structure, while in this embodiment, the drift oxide region 34 is a chemical vapor deposition (chemical vapor deposition, CVD) oxide region. The CVD oxide region is formed by a CVD process deposition step. CVD deposition is well known to a person having ordinary skill in the art, so the details thereof are not redundantly explained here.
Please refer to FIG. 4 which shows a third embodiment of the present invention. FIG. 4 shows a schematic of a cross-section view of a high voltage device 400. As shown in FIG. 4, the high voltage device 400 includes a semiconductor layer 41′, a deep well 411, a buried layer 412, a first high voltage well 42, an isolation structure 43, a drift oxide region 44, a deep well column 45, a body region 46, a body contact 46′, a gate 47, a source 48, a drain 49, a first conductivity type well 411′, a first conductivity type contact 411″, a second high voltage well 412′, and a second conductivity type contact 412″.
