How to remove the transparency of the grass ? (with terrain tool)

Hello,

I painted grass with the Unity terrain tool. My problem is that the grass is slightly transparent. On the screen you can see through the grass the edge of the terrain and some assets:

I would like to know if there is a possibility to make it opaque? (I specify that I have no experience about shader.)

• My grass is a texture and not a mesh.

• The billboard box is not checked.

• The texture is in PNG

Thank you in advance for your answers