Problem with the movement of AI

I have made an IA that follow me when he see me. Instead of just following me, he follow me and he goes up. I don't know what to do.

The following file is the file that control the Mob.

File : EnemyScript.js

 var hitPoints = 100;
 var explosion:Transform;
 
 var gravity=20;
 var characterLayer:LayerMask;
 private var player:GameObject;
 player=GameObject.Find("Player");
 
 var visionAngle:float = 45;
 var visionRange:float = 100;
 private var distanceToPlayer:float;
 private var canSeePlayer:boolean=false;
 
 var hit:RaycastHit;
 
 function Update() {
     seekPlayer();
 }
 
 function seekPlayer() {
     directionToPlayer = player.transform.position - transform.position;
     distanceToPlayer = Vector3.Distance(transform.position, player.transform.position);
     
     var playerAngle = Vector3.Angle(directionToPlayer, transform.forward);
     
     if (Mathf.Abs(playerAngle) < visionAngle && distanceToPlayer < visionRange)/* || canSeePlayer == true)*/ {
         Physics.Linecast(transform.position, player.transform.position, hit, ~characterLayer.value); 
         
         if (hit.collider.name==player.collider.name) {
             var moveDirection = transform.forward;
             var tempRot = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(directionToPlayer), 2 * Time.deltaTime);
             tempRot.x = 0;
             tempRot.z = 0;
             transform.rotation = tempRot;
             canSeePlayer = true;
         }
     }
     
     moveDirection.y -= gravity * Time.deltaTime;
     var controller:CharacterController=GetComponent(CharacterController);
     controller.Move(moveDirection * 3 * Time.deltaTime);
 }
 
 
 function makeDamage(damage:float) {
     hitPoints -= damage;
     
     if (hitPoints <= 0) {
         Instantiate(explosion, transform.position, transform.rotation);
         Destroy(gameObject);
     }
 }

If you need other information to help me, just ask, I'll try to find them.