Border-Radius没有正确对齐

I am trying to create a div with rounded corners. Inside this div contains additional content that will fill up the height of this div. I've noticed that there is some visual corruption at each corner of the rounded div. It looks to me that the corner of the outer div is lightly larger than the inner div. According to my code, the border-radius of both divs should be identical.I am trying to create a div with rounded corner