Semiconductor device and method for manufacturing semiconductor device

Abstract

A semiconductor device with favorable electrical characteristics is provided. A highly reliable semiconductor device is provided. The semiconductor device includes a semiconductor layer, a first insulating layer over the semiconductor layer, and a conductive layer over the first insulating layer. The semiconductor layer includes a first region, a pair of second regions, a pair of third regions, and a pair of fourth regions. The second regions sandwich the first region, the third regions sandwich the first region and the second regions, and the fourth regions sandwich the first region, the second regions, and the third regions. The first region includes a region overlapping with the first insulating layer and the conductive layer, the second regions and the third regions each include a region overlapping with the first insulating layer and not overlapping with the conductive layer, and the fourth regions overlap with neither the first insulating layer nor the conductive layer. A thickness of the first insulating layer in regions overlapping with the second regions is substantially equal to a thickness of the first insulating layer in a region overlapping with the first region. A thickness of the first insulating layer in regions overlapping with the third regions is smaller than the thickness of the first insulating layer in the regions overlapping with the second regions.