How about this, via pstricks package \usepackage{pstricks} .. .. \begingroup \renewcommand*{\arraystretch}{1.5} \[ \left[ \begin{array}{cccc} 0&0&\cdots&0\\ 0&0&\rnode[lc]{c}{\cdots}&0\\ % <-- \rnode means reference node \vdots&\vdots&\ddots&\vdots\\ 0&0&\cdots&0\\ \end{array} \right] \] \psellipse[linecolor=red](c)(1.2,0.4) % <-- (r1=1.2, r2=0.4) \endgroup The basic idea is to define a reference node c, via pstrick command \ronde and then define the command \psellipse which requires a center point and radii r1 and r2. If not familiar with the pstricks, please Google search "pstricks user's guide" and download it for details. Comments: 1. Obviously, the result is not perfect and improvement is possible. This is because the center point c is not easy to identify in this case. 2. To improve that, you can use \psframe command to generate a box with rounded corners which will have a much pleasant look (My guess is this would be what you want.) To that end, I will leave it to you. 3. Happy TeXploring