FollowCharacter.cs

// Attach to camera to have it follow a GameObject in Unity 2d

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class FollowCharacter : MonoBehaviour
{
    public float interpolationSpeed = 0.5f;
    public float verticalOffset = 4.0f;
    public GameObject focusObject;
    void Start()
    {
        focusObject = GameObject.Find("Mario");
    }
    void LateUpdate()
    {
        Vector3 targetPosition = new Vector3(
            focusObject.transform.position.x, 
            focusObject.transform.position.y + verticalOffset, 
            transform.position.z);
        transform.position = Vector3.Lerp(transform.position, targetPosition, interpolationSpeed);
    }
}