Methods of forming a high sensitivity Hall effect sensor having a thin Hall plate and the resulting devices are provided. Embodiments include providing a SOI substrate having a sequentially formed Si substrate and BOX and Si layers; forming a first STI structure in a first portion of the Si layer above the BOX layer, the first STI structure having a cross-shaped pattern; forming a second STI structure in a frame-shaped pattern in a second portion of the Si layer; the second STI structure formed outside and adjacent to the first STI structure; removing a portion of the Si layer between the first and second STI structures down to the BOX layer; removing the first STI structure, a cross-shaped Si layer remaining; and implanting N+ dopant ions into each end of the cross-shaped Si layer to form N+ implantation regions.