How remove block mesh gap

I'm creating a minecraft based world, but i came across a problem.
When I generate the world, it becomes like the image with this little gap between blocks.
How i remove it?

I'm creating each quad individually and then combining it in a single chunk.

This is the code used to combine:

 private void CombineQuads()
 {
     var meshFilters = Object.GetComponentsInChildren<MeshFilter>();
     var combine = new CombineInstance[meshFilters.Length];
 
     for (int i = 0; i < meshFilters.Length; i++)
     {
         combine[i].mesh = meshFilters[i].sharedMesh;
         combine[i].transform = meshFilters[i].transform.localToWorldMatrix;
     }
 
     var mf = Object.AddComponent<MeshFilter>();
     mf.mesh = new Mesh();
 
     mf.mesh.CombineMeshes(combine);
 
     MeshRenderer renderer = Object.AddComponent<MeshRenderer>();
     renderer.material = TextureAtlas;
 
     foreach (Transform quad in Object.transform)
     {
         GameObject.Destroy(quad.gameObject);
     }
 }

And this what i use to create each single quad:

 private void CreateQuad(CubeSide side)
 {
     var mesh = new Mesh
     {
         name = side.ToString() + "QuadMesh",
     };
 
     var p0 = new Vector3(-0.5f, -0.5f, 0.5f);
     var p1 = new Vector3(0.5f, -0.5f, 0.5f);
     var p2 = new Vector3(0.5f, -0.5f, -0.5f);
     var p3 = new Vector3(-0.5f, -0.5f, -0.5f);
     var p4 = new Vector3(-0.5f, 0.5f, 0.5f);
     var p5 = new Vector3(0.5f, 0.5f, 0.5f);
     var p6 = new Vector3(0.5f, 0.5f, -0.5f);
     var p7 = new Vector3(-0.5f, 0.5f, -0.5f);
 
     switch (side)
     {
         case CubeSide.Bottom:
             mesh.vertices = new Vector3[] { p0, p1, p2, p3 };
             mesh.normals = new Vector3[] {Vector3.down, Vector3.down,
                                     Vector3.down, Vector3.down};
             break;
         case CubeSide.Top:
             mesh.vertices = new Vector3[] { p7, p6, p5, p4 };
             mesh.normals = new Vector3[] {Vector3.up, Vector3.up,
                                     Vector3.up, Vector3.up};
             break;
         case CubeSide.Left:
             mesh.vertices = new Vector3[] { p7, p4, p0, p3 };
             mesh.normals = new Vector3[] {Vector3.left, Vector3.left,
                                     Vector3.left, Vector3.left};
             break;
         case CubeSide.Right:
             mesh.vertices = new Vector3[] { p5, p6, p2, p1 };
             mesh.normals = new Vector3[] {Vector3.right, Vector3.right,
                                     Vector3.right, Vector3.right};
             break;
         case CubeSide.Front:
             mesh.vertices = new Vector3[] { p4, p5, p1, p0 };
             mesh.normals = new Vector3[] {Vector3.forward, Vector3.forward,
                                     Vector3.forward, Vector3.forward};
             break;
         case CubeSide.Back:
             mesh.vertices = new Vector3[] { p6, p7, p3, p2 };
             mesh.normals = new Vector3[] {Vector3.back, Vector3.back,
                                     Vector3.back, Vector3.back};
             break;
     }
 
     mesh.uv = Block.UVs.TryGetValue(side, CubeSide.Front).ToArray();
     mesh.triangles = new int[] { 3, 1, 0, 3, 2, 1 };
 
     mesh.RecalculateBounds();
 
     var quad = new GameObject("Quad");
     quad.transform.parent = Parent.Object.transform;
     quad.transform.position = Position;
 
     var meshFilter = quad.AddComponent<MeshFilter>();
     meshFilter.mesh = mesh;
 }